ROLLOUT 3 · narwhals-dev/narwhals
narwhals-dev__narwhals-2864
Solved
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16tool calls
18model calls
5,983tokens generated
167,664prompt tokens read
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⚠ The request log has 17 model calls but the trace has 19 agent calls, so tokens are listed separately instead of beside each turn.
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System instructions 4,822 characters
You are a principal Python software engineer resolving a repository issue in `/workspace`. Your sole objective is to produce a minimal, root-cause source patch that passes every hidden fail-to-pass and pass-to-pass regression test on the first grading run. ## Critical Environment & Grader Rules 1. **Air-Gapped Sandbox & Available CLI Tools**: No network access. Never run `pip`, `uv`, `conda`, or `git fetch`. Note: `rg` (`ripgrep`) is NOT installed in the container — always use `grep -rn --include="*.py"` for fast exact searches so you never waste a tool call on `command not found`. 2. **Protected Grading Paths**: Before running official verification, the grading harness **strips and reverts all changes** to `tests/`, `test/`, `testing/`, `test_*.py`, `*_test.py`, `conftest.py`, `pyproject.toml`, `setup.cfg`, `pytest.ini`, and `tox.ini`. Every part of your fix MUST reside in non-test production source files. 3. **Untracked File Trap (`git add -N .`)**: `submit_patch` stages ALL untracked files inside `/workspace`! Never leave reproduction or scratch files inside `/workspace` — run reproductions inline via `python3 - <<'PY'` or inside `/tmp/repro.py` in a single `run_command`. 4. **Stdout Truncation Rule**: `run_command` truncates stdout after the first 5,000 characters from the TOP. Always run pytest quietly with short tracebacks: `pytest path/to/test_file.py -k pattern -q --tb=short --no-header` If a test file is large, redirect output to `/tmp/pytest.log` and inspect `tail -n 80 /tmp/pytest.log` so failure tracebacks at the bottom are never cut off. 5. **Strict Pacing Discipline**: `get_status` and `submit_patch` are free and do NOT count toward `max_tool_calls`. Target **16-22 counted tool calls total**, and **begin your first `edit_file` change no later than tool call 15**. Reserve at least 4 calls for verification, `git status --short && git diff`, and submission. ## Execution Protocol ### Phase 1 — Pinpoint Code & Tests Immediately (1-2 tool calls) - The user message already contains `Workspace Layout` — do NOT waste a turn running `ls` on top-level directories. - Run a single compound `run_command` with `grep -rn --include="*.py"` to locate: (a) the exact symbols, error strings, or functions from the problem description, (b) **all parallel or sibling implementations** (for example sync + async variants, `Client` + `AsyncClient`, serializer + deserializer, multiple backends/dialects, base + subclass methods, `__init__.py` / `__all__` exports), and (c) the closest existing unit test files under `tests/`. ### Phase 2 — Deep Read & Spec Anchor (2-5 tool calls) - Use `read_file` with generous `start_line` and `end_line` windows (180-300 lines per call so you read whole modules in fewer calls) on the target function/class, callers, type annotations, and neighboring tests. - Before editing, verify every explicit and implicit requirement from the issue: exact parameter names, defaults, boundary/domain edge cases, exception types/messages, `None` vs empty collection vs falsy (`0`, `False`, `""`) semantics, mutability/copying, and return types. ### Phase 3 — Reproduce Bug in One Call (1 tool call) - Run ONE concise command (`python3 - <<'PY' ... PY` or targeted `pytest ... -q --tb=short --no-header`) via `run_command` to observe the exact pre-fix failure. Do NOT spend multiple tool calls writing separate reproduction scripts. ### Phase 4 — Surgical Implementation Across All Parallel Paths (1-4 tool calls) - Begin editing by tool call 15! Use `edit_file` with 4-6 lines of exact surrounding context copied from `read_file`. - Update ALL parallel codepaths (sync/async, multiple classes/dialects, type hints) consistently so partial fixes do not fail sibling tests. - **2-Strike Edit Rule**: If `edit_file` fails twice on the same block due to whitespace or escaping, do not retry `edit_file` a third time — apply an atomic Python transformation via `run_command` and immediately verify `python3 -m py_compile path/to/file.py`. ### Phase 5 — Edge-Case Verification, Diff Hygiene & Clean Exit (2-4 tool calls) - Run a single compound `run_command` testing both your reproduction + boundary edge cases (`None`, empty input, leading/trailing delimiters, subdomain/prefix boundaries, subclass/async parity) AND the relevant existing `pytest` module(s) with `-q --tb=short --no-header`. - Run `git status --short && git diff` via `run_command`. Confirm: - ZERO untracked (`??`) files in `/workspace` (`rm -f` any untracked workspace files immediately), - ZERO modifications to `tests/` or protected config files (`git checkout -- tests/` if touched), - Minimal, clean diff with valid imports and indentation. - Call `submit_patch` once verification passes, then respond with a brief 2-sentence plain-text summary and make NO further tool calls.
Task prompt 7,523 characters
You are evaluating a software engineering task for repository narwhals-dev/narwhals.
Problem Statement:
bug: `ArrowSeries.scatter` raises out of bound error
pyarrow backed series raises an out of bound error in scatter if `indices`:
- is not 0
- are not full length of the series
Repro:
```py
import narwhals as nw
import pyarrow as pa
tbl = pa.table({"a": [1, 2, 3], "b": [142, 124, 132]})
frame = nw.from_native(tbl, eager_only=True)
ser = frame["a"]
try:
result = ser.scatter(1, 999)
except Exception as exc:
print(exc)
try:
result = ser.scatter([0, 2], [999, 888])
except Exception as exc:
print(exc)
```
> Index 1 out of bounds
> Index 2 out of bounds
## Task Budget (Session terminates when any budget is exhausted)
- Time allowance: 7.5 minutes
- Tool calls allowance: 30 calls
- Max loop iterations: 40 turns
## Execution Environment Rules
- Single command timeout: 90 seconds (commands exceeding this fail without ending the session)
- Command output limit: 5000 characters
- File view limit: 150 lines per read_file call
- File character limit: 10000 characters per read_file call
- Environment is offline (no network/PyPI access). All repository and test dependencies are ALREADY pre-installed. Do NOT attempt to run pip install or download packages.
## Instructions:
0. All source code is under `/workspace`. Do NOT search outside `/workspace` (e.g. `/usr/`, `/wheels/`, system site-packages). If imports fail, the issue is in the source code under `/workspace`, not in missing system packages.
1. Analyze the problem statement and any provided hints carefully to identify all requested script paths, CLI subcommands, or Python modules.
2. Inspect existing codebase conventions and test files before making edits.
3. Verify your implementation using targeted tests or inline assertions before submitting.
4. Call submit_patch only after your implementation is complete and verified.
5. As your final action, you must return a text-only response reporting your completion to terminate the session.
## Workspace Layout
The repository is located at `/workspace`. Here is the directory tree (up to 3 levels):
```
./CONTRIBUTING.md
./LICENSE.md
./Makefile
./README.md
./docs
./docstring_template.mustache
./mkdocs.yml
./narwhals
./narwhals/__init__.py
./narwhals/_arrow
./narwhals/_arrow/__init__.py
./narwhals/_arrow/dataframe.py
./narwhals/_arrow/expr.py
./narwhals/_arrow/group_by.py
./narwhals/_arrow/namespace.py
./narwhals/_arrow/selectors.py
./narwhals/_arrow/series.py
./narwhals/_arrow/series_cat.py
./narwhals/_arrow/series_dt.py
./narwhals/_arrow/series_list.py
./narwhals/_arrow/series_str.py
./narwhals/_arrow/series_struct.py
./narwhals/_arrow/typing.py
./narwhals/_arrow/utils.py
./narwhals/_compliant
./narwhals/_compliant/__init__.py
./narwhals/_compliant/any_namespace.py
./narwhals/_compliant/dataframe.py
./narwhals/_compliant/expr.py
./narwhals/_compliant/group_by.py
./narwhals/_compliant/namespace.py
./narwhals/_compliant/selectors.py
./narwhals/_compliant/series.py
./narwhals/_compliant/typing.py
./narwhals/_compliant/when_then.py
./narwhals/_compliant/window.py
./narwhals/_constants.py
./narwhals/_dask
./narwhals/_dask/__init__.py
./narwhals/_dask/dataframe.py
./narwhals/_dask/expr.py
./narwhals/_dask/expr_dt.py
./narwhals/_dask/expr_str.py
./narwhals/_dask/group_by.py
./narwhals/_dask/namespace.py
./narwhals/_dask/selectors.py
./narwhals/_dask/utils.py
./narwhals/_duckdb
./narwhals/_duckdb/__init__.py
./narwhals/_duckdb/dataframe.py
./narwhals/_duckdb/expr.py
./narwhals/_duckdb/expr_dt.py
./narwhals/_duckdb/expr_list.py
./narwhals/_duckdb/expr_str.py
./narwhals/_duckdb/expr_struct.py
./narwhals/_duckdb/group_by.py
./narwhals/_duckdb/namespace.py
./narwhals/_duckdb/selectors.py
./narwhals/_duckdb/series.py
./narwhals/_duckdb/typing.py
./narwhals/_duckdb/utils.py
./narwhals/_duration.py
./narwhals/_enum.py
./narwhals/_expression_parsing.py
./narwhals/_ibis
./narwhals/_ibis/__init__.py
./narwhals/_ibis/dataframe.py
./narwhals/_ibis/expr.py
./narwhals/_ibis/expr_dt.py
./narwhals/_ibis/expr_list.py
./narwhals/_ibis/expr_str.py
./narwhals/_ibis/expr_struct.py
./narwhals/_ibis/group_by.py
./narwhals/_ibis/namespace.py
./narwhals/_ibis/selectors.py
./narwhals/_ibis/series.py
./narwhals/_ibis/utils.py
./narwhals/_interchange
./narwhals/_interchange/__init__.py
./narwhals/_interchange/dataframe.py
./narwhals/_interchange/series.py
./narwhals/_namespace.py
./narwhals/_pandas_like
./narwhals/_pandas_like/__init__.py
./narwhals/_pandas_like/dataframe.py
./narwhals/_pandas_like/expr.py
./narwhals/_pandas_like/group_by.py
./narwhals/_pandas_like/namespace.py
./narwhals/_pandas_like/selectors.py
./narwhals/_pandas_like/series.py
./narwhals/_pandas_like/series_cat.py
./narwhals/_pandas_like/series_dt.py
./narwhals/_pandas_like/series_list.py
./narwhals/_pandas_like/series_str.py
./narwhals/_pandas_like/series_struct.py
./narwhals/_pandas_like/typing.py
./narwhals/_pandas_like/utils.py
./narwhals/_polars
./narwhals/_polars/__init__.py
./narwhals/_polars/dataframe.py
./narwhals/_polars/expr.py
./narwhals/_polars/group_by.py
./narwhals/_polars/namespace.py
./narwhals/_polars/series.py
./narwhals/_polars/typing.py
./narwhals/_polars/utils.py
./narwhals/_spark_like
./narwhals/_spark_like/__init__.py
./narwhals/_spark_like/dataframe.py
./narwhals/_spark_like/expr.py
./narwhals/_spark_like/expr_dt.py
./narwhals/_spark_like/expr_list.py
./narwhals/_spark_like/expr_str.py
./narwhals/_spark_like/expr_struct.py
./narwhals/_spark_like/group_by.py
./narwhals/_spark_like/namespace.py
./narwhals/_spark_like/selectors.py
./narwhals/_spark_like/utils.py
./narwhals/_sql
./narwhals/_sql/__init__.py
./narwhals/_sql/dataframe.py
./narwhals/_sql/expr.py
./narwhals/_sql/group_by.py
./narwhals/_sql/typing.py
./narwhals/_sql/when_then.py
./narwhals/_translate.py
./narwhals/_typing_compat.py
./narwhals/_utils.py
./narwhals/dataframe.py
./narwhals/dependencies.py
./narwhals/dtypes.py
./narwhals/exceptions.py
./narwhals/expr.py
./narwhals/expr_cat.py
./narwhals/expr_dt.py
./narwhals/expr_list.py
./narwhals/expr_name.py
./narwhals/expr_str.py
./narwhals/expr_struct.py
./narwhals/functions.py
./narwhals/group_by.py
./narwhals/py.typed
./narwhals/schema.py
./narwhals/selectors.py
./narwhals/series.py
./narwhals/series_cat.py
./narwhals/series_dt.py
./narwhals/series_list.py
./narwhals/series_str.py
./narwhals/series_struct.py
./narwhals/stable
./narwhals/stable/__init__.py
./narwhals/stable/v1
./narwhals/this.py
./narwhals/translate.py
./narwhals/typing.py
./narwhals/utils.py
./noxfile.py
./pyproject.toml
./tests
./tpch
./tpch/README.md
./tpch/__init__.py
./tpch/execute.py
./tpch/generate_data.py
./tpch/queries
./tpch/queries/__init__.py
./tpch/queries/q1.py
./tpch/queries/q10.py
./tpch/queries/q11.py
./tpch/queries/q12.py
./tpch/queries/q13.py
./tpch/queries/q14.py
./tpch/queries/q15.py
./tpch/queries/q16.py
./tpch/queries/q17.py
./tpch/queries/q18.py
./tpch/queries/q19.py
./tpch/queries/q2.py
./tpch/queries/q20.py
./tpch/queries/q21.py
./tpch/queries/q22.py
./tpch/queries/q3.py
./tpch/queries/q4.py
./tpch/queries/q5.py
./tpch/queries/q6.py
./tpch/queries/q7.py
./tpch/tests
./utils
./utils/__init__.py
./utils/api-completeness.md.jinja
./utils/bump_version.py
./utils/check_api_reference.py
./utils/check_dist_content.py
./utils/check_docstrings.py
./utils/check_for_no_build_errors.py
./utils/generate_backend_completeness.py
./utils/generate_random_versions.py
./utils/generate_zen_content.py
./utils/import_check.py
```
Turn 1at 23 s335 tokens out4,792 prompt tokens
The user is reporting a bug in `ArrowSeries.scatter` where it raises an "out of bound" error when `indices` is not 0 or not the full length of the series.
Looking at the provided repro:
```python
import narwhals as nw
import pyarrow as pa
tbl = pa.table({"a": [1, 2, 3], "b": [142, 124, 132]})
frame = nw.from_native(tbl, eager_only=True)
ser = frame["a"]
try:
result = ser.scatter(1, 999)
except Exception as exc:
print(exc)
try:
result = ser.scatter([0, 2], [999, 888])
except Exception as exc:
print(exc)
```
The output is:
`Index 1 out of bounds`
`Index 2 out of bounds`
This looks like it's coming from the pyarrow backend implementation of `scatter`.
I need to find where `scatter` is implemented for `ArrowSeries`.
Based on the workspace layout:
`./narwhals/_arrow/series.py` seems like the most likely place.
Let's start by searching for `scatter` in `narwhals/_arrow/series.py`.
TOOL CALL · run_command
{
"command": "grep -rn --include=\"*.py\" \"def scatter\" narwhals/"
}Result of run_command 593 characters
{
"status": "ok",
"stdout": "narwhals/_compliant/series.py:251: def scatter(self, indices: int | Sequence[int], values: Any) -> Self: ...\nnarwhals/series.py:238: def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\nnarwhals/_pandas_like/series.py:273: def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\nnarwhals/_arrow/series.py:440: def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\nnarwhals/_polars/series.py:432: def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\n",
"stderr": "",
"exit_code": 0
}Turn 2at 31 s100 tokens out5,349 prompt tokens
Okay, I see `scatter` implemented in several places. The report specifically mentions pyarrow backed series, so `narwhals/_arrow/series.py` is the target. Let's examine the implementation of `scatter` in `narwhals/_arrow/series.py`.
TOOL CALL · read_file
{
"end_line": 470,
"filepath": "narwhals/_arrow/series.py",
"start_line": 400
}Result of read_file 3,261 characters
{
"status": "ok",
"filepath": "narwhals/_arrow/series.py",
"content": " return maybe_extract_py_scalar(k, _return_py_scalar)\n\n def count(self, *, _return_py_scalar: bool = True) -> int:\n return maybe_extract_py_scalar(pc.count(self.native), _return_py_scalar)\n\n def n_unique(self, *, _return_py_scalar: bool = True) -> int:\n return maybe_extract_py_scalar(\n pc.count(self.native.unique(), mode=\"all\"), _return_py_scalar\n )\n\n def __native_namespace__(self) -> ModuleType:\n if self._implementation is Implementation.PYARROW:\n return self._implementation.to_native_namespace()\n\n msg = f\"Expected pyarrow, got: {type(self._implementation)}\" # pragma: no cover\n raise AssertionError(msg)\n\n @property\n def name(self) -> str:\n return self._name\n\n def _gather(self, rows: SizedMultiIndexSelector[ChunkedArrayAny]) -> Self:\n if len(rows) == 0:\n return self._with_native(self.native.slice(0, 0))\n if self._backend_version < (18,) and isinstance(rows, tuple):\n rows = list(rows)\n return self._with_native(self.native.take(rows))\n\n def _gather_slice(self, rows: _SliceIndex | range) -> Self:\n start = rows.start or 0\n stop = rows.stop if rows.stop is not None else len(self.native)\n if start < 0:\n start = len(self.native) + start\n if stop < 0:\n stop = len(self.native) + stop\n if rows.step is not None and rows.step != 1:\n msg = \"Slicing with step is not supported on PyArrow tables\"\n raise NotImplementedError(msg)\n return self._with_native(self.native.slice(start, stop - start))\n\n def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\n import numpy as np # ignore-banned-import\n\n values_native: ArrayAny\n if isinstance(indices, int):\n indices_native = pa.array([indices])\n values_native = pa.array([values])\n else:\n # TODO(unassigned): we may also want to let `indices` be a Series.\n # https://github.com/narwhals-dev/narwhals/issues/2155\n indices_native = pa.array(indices)\n if isinstance(values, self.__class__):\n values_native = values.native.combine_chunks()\n else:\n # NOTE: Requires fixes in https://github.com/zen-xu/pyarrow-stubs/pull/209\n pa_array: Incomplete = pa.array\n values_native = pa_array(values)\n\n sorting_indices = pc.sort_indices(indices_native)\n indices_native = indices_native.take(sorting_indices)\n values_native = values_native.take(sorting_indices)\n\n mask: _1DArray = np.zeros(self.len(), dtype=bool)\n mask[indices_native] = True\n # NOTE: Multiple issues\n # - Missing `values` type\n # - `mask` accepts a `np.ndarray`, but not mentioned in stubs\n # - Missing `replacements` type\n # - Missing return type\n pc_replace_with_mask: Incomplete = pc.replace_with_mask\n return self._with_native(",
"start_line": 400,
"end_line": 470,
"total_lines": 1170,
"is_truncated": false
}Turn 3at 36 s86 tokens out6,430 prompt tokens
Wait, the `read_file` output is truncated? No, it says `is_truncated: false`, but the code ends with `return self._with_native(`. Let me read more of `scatter`.
TOOL CALL · read_file
{
"end_line": 480,
"filepath": "narwhals/_arrow/series.py",
"start_line": 460
}Result of read_file 1,038 characters
{
"status": "ok",
"filepath": "narwhals/_arrow/series.py",
"content": " values_native = values_native.take(sorting_indices)\n\n mask: _1DArray = np.zeros(self.len(), dtype=bool)\n mask[indices_native] = True\n # NOTE: Multiple issues\n # - Missing `values` type\n # - `mask` accepts a `np.ndarray`, but not mentioned in stubs\n # - Missing `replacements` type\n # - Missing return type\n pc_replace_with_mask: Incomplete = pc.replace_with_mask\n return self._with_native(\n pc_replace_with_mask(self.native, mask, values_native.take(indices_native))\n )\n\n def to_list(self) -> list[Any]:\n return self.native.to_pylist()\n\n def __array__(self, dtype: Any = None, *, copy: bool | None = None) -> _1DArray:\n return self.native.__array__(dtype=dtype, copy=copy)\n\n def to_numpy(self, dtype: Any = None, *, copy: bool | None = None) -> _1DArray:",
"start_line": 460,
"end_line": 480,
"total_lines": 1170,
"is_truncated": false
}Turn 4at 98 s1,003 tokens out6,868 prompt tokens
Wait, look at this line:
`return self._with_native(pc_replace_with_mask(self.native, mask, values_native.take(indices_native)))`
`indices_native` are the indices we want to replace.
`values_native` are the new values.
`mask` is a boolean array of the same size as `self.native`, where it's `True` at `indices_native`.
The problem is `values_native.take(indices_native)`.
If `indices_native` are `[1]`, and `values_native` is `[999]`, then `values_native.take(indices_native)` will try to take the element at index 1 from `values_native`, which only has one element at index 0. This is why it's raising "out of bound error".
`values_native` should already be the values to put at `indices_native`.
Let's re-examine:
```python
if isinstance(indices, int):
indices_native = pa.array([indices])
values_native = pa.array([values])
else:
# TODO(unassigned): we may also want to let `indices` be a Series.
# https://github.com/narwhals-dev/narwhals/issues/2155
indices_native = pa.array(indices)
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
else:
# NOTE: Requires fixes in https://github.com/zen-xu/pyarrow-stubs/pull/209
pa_array: Incomplete = pa.array
values_native = pa_array(values)
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
Here `indices_native` and `values_native` are aligned.
Then:
```python
mask: _1DArray = np.zeros(self.len(), dtype=bool)
mask[indices_native] = True
# ...
return self._with_native(
pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
)
```
The `pc.replace_with_mask` takes:
1. The original array.
2. A boolean mask (where to replace).
3. The replacements.
According to pyarrow's `replace_with_mask` (or rather `pc.replace_with_mask` wrapper if it exists, though it might be `pc.replace_with_mask` in newer versions of pyarrow, or something else), the third argument should be the array of replacements.
If we have:
`self.native` = `[1, 2, 3]`
`indices` = `[0, 2]`
`values` = `[999, 888]`
`mask` = `[True, False, True]`
`values_native` = `[999, 888]`
`values_native.take(indices_native)` will try to do `[999, 888].take([0, 2])`, which fails because index 2 is out of bounds for `[999, 888]`.
It should just be `values_native`.
Let's verify this by running the repro.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport narwhals as nw\nimport pyarrow as pa\n\ntbl = pa.table({\"a\": [1, 2, 3], \"b\": [142, 124, 132]})\nframe = nw.from_native(tbl, eager_only=True)\nser = frame[\"a\"]\n\ntry:\n result = ser.scatter(1, 999)\n print(\"Success 1:\", result)\nexcept Exception as exc:\n print(\"Error 1:\", exc)\n\n\ntry:\n result = ser.scatter([0, 2], [999, 888])\n print(\"Success 2:\", result)\nexcept Exception as exc:\n print(\"Error 2:\", exc)\nPY\n"
}Result of run_command 124 characters
{
"status": "ok",
"stdout": "Error 1: Index 1 out of bounds\nError 2: Index 2 out of bounds\n",
"stderr": "",
"exit_code": 0
}Turn 5at 124 s304 tokens out7,933 prompt tokens
Exactly as reported. The fix should be to remove `.take(indices_native)` from the last line. Wait, let me check the documentation for `pc.replace_with_mask` if possible, or just deduce it. If `mask` has `N` True values, then the replacements array should probably have `N` values? Or should it be the same length as the original array? Actually, in PyArrow's `compute.replace_with_mask`, the `replacements` array must be the same length as the original array? No, that's usually not how it works for masks. Wait, I should check how `pc.replace_with_mask` works in pyarrow. Since I don't have internet, I'll test it in a small script.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport pyarrow as pa\nimport pyarrow.compute as pc\nimport numpy as np\n\narr = pa.array([1, 2, 3])\nmask = np.array([True, False, True])\nreplacements = pa.array([999, 888])\n\ntry:\n res = pc.replace_with_mask(arr, mask, replacements)\n print(\"Result:\", res)\nexcept Exception as e:\n print(\"Error:\", e)\nPY\n"
}Result of run_command 95 characters
{
"status": "ok",
"stdout": "Result: [\n 999,\n 2,\n 888\n]\n",
"stderr": "",
"exit_code": 0
}Turn 6at 159 s445 tokens out8,297 prompt tokens
Yes, `replacements` should be an array containing only the values for the `True` positions in the mask, in the order they appear in the original array.
In the `scatter` implementation:
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
This part ensures that `indices_native` are sorted and `values_native` are sorted accordingly.
Then `mask` is created:
```python
mask: _1DArray = np.zeros(self.len(), dtype=bool)
mask[indices_native] = True
```
So `indices_native` tells us where the True valeurs are in `mask`, in increasing order.
And `values_native` contains the replacement values for those indices, also in increasing order of index.
So `pc_replace_with_mask(self.native, mask, values_native)` is exactly what is needed.
Let's check if there are any other parallel implementations of `scatter` that might need similar fixes.
I saw:
- `narwhals/_compliant/series.py`
- `narwhals/series.py`
- `narwhals/_pandas_like/series.py`
- `narwhals/_polars/series.py`
But `narwhals/series.py` is likely the public API that delegates to the backend.
`narwhals/_compliant/series.py` is probably for compliance tests.
`narwhals/_pandas_like/series.py` might be a common base or similar.
`narwhals/_polars/series.py` is the Polars backend.
Let's check `narwhals/series.py`.
TOOL CALL · read_file
{
"end_line": 250,
"filepath": "narwhals/series.py",
"start_line": 220
}Result of read_file 1,180 characters
{
"status": "ok",
"filepath": "narwhals/series.py",
"content": " Series of class that user started with.\n\n Examples:\n >>> import polars as pl\n >>> import narwhals as nw\n >>>\n >>> s_native = pl.Series([1, 2])\n >>> s = nw.from_native(s_native, series_only=True)\n >>> s.to_native() # doctest: +NORMALIZE_WHITESPACE\n shape: (2,)\n Series: '' [i64]\n [\n 1\n 2\n ]\n \"\"\"\n return self._compliant_series.native\n\n def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\n \"\"\"Set value(s) at given position(s).\n\n Arguments:\n indices: Position(s) to set items at.\n values: Values to set.\n\n Returns:\n A new Series with values set at given positions.\n\n Note:\n This method always returns a new Series, without modifying the original one.\n Using this function in a for-loop is an anti-pattern, we recommend building",
"start_line": 220,
"end_line": 250,
"total_lines": 2699,
"is_truncated": false
}Turn 7at 171 s152 tokens out9,091 prompt tokens
`narwhals/series.py` just defines the interface and presumably delegates. Let's see how it does that. Wait, the layout says `narwhals/series.py` is the main Series class. But I don't see how it calls the backend in the snippet. Wait, `narwhals` usually works by translating high-level calls to backend-specific calls. Let's check `narwhals/_polars/series.py` to see if it has a similar bug.
TOOL CALL · read_file
{
"end_line": 450,
"filepath": "narwhals/_polars/series.py",
"start_line": 420
}Result of read_file 1,491 characters
{
"status": "ok",
"filepath": "narwhals/_polars/series.py",
"content": " def sort(self, *, descending: bool, nulls_last: bool) -> Self:\n if self._backend_version < (0, 20, 6):\n result = self.native.sort(descending=descending)\n\n if nulls_last:\n is_null = result.is_null()\n result = pl.concat([result.filter(~is_null), result.filter(is_null)])\n else:\n result = self.native.sort(descending=descending, nulls_last=nulls_last)\n\n return self._with_native(result)\n\n def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\n s = self.native.clone().scatter(indices, extract_native(values))\n return self._with_native(s)\n\n def value_counts(\n self, *, sort: bool, parallel: bool, name: str | None, normalize: bool\n ) -> PolarsDataFrame:\n from narwhals._polars.dataframe import PolarsDataFrame\n\n if self._backend_version < (1, 0, 0):\n value_name_ = name or (\"proportion\" if normalize else \"count\")\n\n result = self.native.value_counts(sort=sort, parallel=parallel).select(\n **{\n (self.native.name): pl.col(self.native.name),\n value_name_: pl.col(\"count\") / pl.sum(\"count\")\n if normalize\n else pl.col(\"count\"),\n }",
"start_line": 420,
"end_line": 450,
"total_lines": 741,
"is_truncated": false
}Turn 8at 177 s75 tokens out9,705 prompt tokens
Polars implementation is very different and leverages Polars' own `scatter`. What about `narwhals/_pandas_like/series.py`?
TOOL CALL · read_file
{
"end_line": 300,
"filepath": "narwhals/_pandas_like/series.py",
"start_line": 260
}Result of read_file 1,944 characters
{
"status": "ok",
"filepath": "narwhals/_pandas_like/series.py",
"content": " else:\n msg = (\n \"cuDF only supports `ewm_mean` when there are no missing values \"\n \"or when both `min_period=0` and `ignore_nulls=False`\"\n )\n raise NotImplementedError(msg)\n else:\n result = ser.ewm(\n com, span, half_life, alpha, min_samples, adjust, ignore_na=ignore_nulls\n ).mean()\n result[mask_na] = None\n return self._with_native(result)\n\n def scatter(self, indices: int | Sequence[int], values: Any) -> Self:\n if isinstance(values, self.__class__):\n values = set_index(\n values.native,\n self.native.index[indices],\n implementation=self._implementation,\n )\n s = self.native.copy(deep=True)\n s.iloc[indices] = values\n s.name = self.name\n return self._with_native(s)\n\n def _scatter_in_place(self, indices: Self, values: Self) -> None:\n implementation = self._implementation\n backend_version = self._backend_version\n # Scatter, modifying original Series. Use with care!\n values_native = set_index(\n values.native,\n self.native.index[indices.native],\n implementation=implementation,\n )\n if implementation is Implementation.PANDAS and parse_version(np) < (2,):\n values_native = values_native.copy() # pragma: no cover\n min_pd_version = (1, 2)\n if implementation is Implementation.PANDAS and backend_version < min_pd_version:\n self.native.iloc[indices.native.values] = values_native # noqa: PD011\n else:\n self.native.iloc[indices.native] = values_native",
"start_line": 260,
"end_line": 300,
"total_lines": 1106,
"is_truncated": false
}Turn 9at 185 s149 tokens out10,326 prompt tokens
This looks like a pandas-like implementation. The bug was specifically for `ArrowSeries`, which is implemented in `narwhals/_arrow/series.py`. Let's apply the fix.
TOOL CALL · edit_file
{
"filepath": "narwhals/_arrow/series.py",
"new_string": " return self._with_native(\n pc_replace_with_mask(self.native, mask, values_native)\n )",
"old_string": " return self._with_native(\n pc_replace_with_mask(self.native, mask, values_native.take(indices_native))\n )"
}Result of edit_file 566 characters
{
"status": "ok",
"filepath": "narwhals/_arrow/series.py",
"occurrences": 1,
"strategy": "exact",
"diff": "--- a/narwhals/_arrow/series.py\n+++ b/narwhals/_arrow/series.py\n@@ -468,7 +468,7 @@\n # - Missing return type\n pc_replace_with_mask: Incomplete = pc.replace_with_mask\n return self._with_native(\n- pc_replace_with_mask(self.native, mask, values_native.take(indices_native))\n+ pc_replace_with_mask(self.native, mask, values_native)\n )\n \n def to_list(self) -> list[Any]:\n",
"is_truncated": false
}Turn 10at 192 s206 tokens out10,685 prompt tokens
Now let's verify with the repro script again.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport narwhals as nw\nimport pyarrow as pa\n\ntbl = pa.table({\"a\": [1, 2, 3], \"b\": [142, 124, 132]})\nframe = nw.from_native(tbl, eager_only=True)\nser = frame[\"a\"]\n\ntry:\n result = ser.scatter(1, 999)\n print(\"Success 1:\", result)\nexcept Exception as exc:\n print(\"Error 1:\", exc)\n\n\ntry:\n result = ser.scatter([0, 2], [999, 888])\n print(\"Success 2:\", result)\nexcept Exception as exc:\n print(\"Error 2:\", exc)\nPY\n"
}Result of run_command 2,462 characters
{
"status": "ok",
"stdout": "Success 1: ┌───────────────────────────────────────────────────┐\n| Narwhals Series |\n|---------------------------------------------------|\n|<pyarrow.lib.ChunkedArray object at 0x7b0b92129840>|\n|[ |\n| [ |\n| 1, |\n| 999, |\n| 3 |\n| ] |\n|] |\n└───────────────────────────────────────────────────┘\nSuccess 2: ┌───────────────────────────────────────────────────┐\n| Narwhals Series |\n|---------------------------------------------------|\n|<pyarrow.lib.ChunkedArray object at 0x7b0b921298a0>|\n|[ |\n| [ |\n| 999, |\n| 2, |\n| 888 |\n| ] |\n|] |\n└───────────────────────────────────────────────────┘\n",
"stderr": "",
"exit_code": 0
}Turn 11at 229 s663 tokens out11,167 prompt tokens
The repro is fixed. Now I should check if there are any other cases to consider.
The indices can be a single integer or a sequence of integers.
What if indices are not sorted?
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
This part handles unsorted indices by sorting both `indices_native` and `values_native` so they align with the mask (which is indexed by `indices_native`).
Wait, let's trace it:
If `indices = [2, 0]` and `values = [888, 999]`
`indices_native` = `[2, 0]`
`values_native` = `[888, 999]`
`sorting_indices` = `[1, 0]` (because `indices_native[1]=0` and `indices_native[0]=2`)
`indices_native` becomes `[0, 2]`
`values_native` becomes `[999, 888]`
Then `mask` becomes `[True, False, True]`
`pc_replace_with_mask(self.native, mask, [999, 888])` will put 999 at index 0 and 888 at index 2. Correct.
What if there are duplicate indices?
`indices = [0, 0]` and `values = [888, 999]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`sorting_indices` = `[0, 1]` or `[1, 0]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`mask` = `[True, False, False]`
`pc_replace_with_mask(self.native, mask, [888, 999])` -> This might actually fail in PyArrow if the replacements array is longer than the number of True values in the mask.
Let's check PyArrow's `pc.replace_with_mask` with duplicate indices.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport pyarrow as pa\nimport pyarrow.compute as pc\nimport numpy as np\n\narr = pa.array([1, 2, 3])\nmask = np.array([True, False, False])\nreplacements = pa.array([888, 999])\n\ntry:\n res = pc.replace_with_mask(arr, mask, replacements)\n print(\"Result:\", res)\nexcept Exception as e:\n print(\"Error:\", e)\nPY\n"
}Result of run_command 93 characters
{
"status": "ok",
"stdout": "Result: [\n 888,\n 2,\n 3\n]\n",
"stderr": "",
"exit_code": 0
}Turn 12at 271 s666 tokens out11,888 prompt tokens
It seems PyArrow just uses the first few elements of `replacements` that match the number of `True` values. Wait, wait. Let's re-read the output: `Result: [888, 2, 3]`. It used 888 at index 0. What if I change the mask to have two True? `mask = np.array([True, True, False])` `replacements = pa.array([888, 999])` Result: `[888, 999, 3]`. So if we have duplicate indices, `mask[indices_native] = True` will only set that position to True once. The `values_native` array will have as many elements as `indices`. If `indices` has duplicates, `len(values_native)` will be greater than `mask.sum()`. The `scatter` behavior in pandas (which narwhals mimics) is that for duplicate indices, the last value wins. Let's see what happens with our current implementation when there are duplicate indices. `indices = [0, 0]`, `values = [888, 999]` `indices_native` = `[0, 0]` `values_native` = `[888, 999]` `sorting_indices` = `[0, 1]` `indices_native` = `[0, 0]` `values_native` = `[888, 999]` `mask` = `[True, False, False]` `pc_replace_with_mask(self.native, mask, [888, 999])` -> Result `[888, 2, 3]`. But it should be `[999, 2, 3]` because the last value for index 0 is 999. Does this matter? The issue description didn't mention duplicate indices, so maybe it's out of scope, but a "principal engineer" would check this. Actually, looking at the current implementation of `scatter` in `_arrow/series.py`, it uses `pc.replace_with_mask`. If we want "last value wins", we might need to avoid duplicates in `indices_native` and only keep the last corresponding value in `values_native`. However, let's check if other backends (like Polars) handle this. Polars `scatter` also handles duplicate indices. Wait, if I'm supposed to provide a MINIMAL root-cause patch, maybe I should just fix the bug reported. The reported bug is: `ArrowSeries.scatter` raises out of bound error when `indices` is not 0 or not full length. The fix I applied addresses this exactly. Let's double check if any existing tests cover `scatter`.
TOOL CALL · run_command
{
"command": "grep -rn \"test_scatter\" tests/"
}Result of run_command 573 characters
{
"status": "ok",
"stdout": "tests/series_only/scatter_test.py:9:def test_scatter(constructor_eager: ConstructorEager) -> None:\ntests/series_only/scatter_test.py:20:def test_scatter_indices() -> None:\ntests/series_only/scatter_test.py:27:def test_scatter_unchanged(constructor_eager: ConstructorEager) -> None:\ntests/series_only/scatter_test.py:48:def test_scatter_integer(constructor_eager: ConstructorEager) -> None:\ntests/series_only/scatter_test.py:58:def test_scatter_unordered_indices(constructor_eager: ConstructorEager) -> None:\n",
"stderr": "",
"exit_code": 0
}Turn 13at 273 s50 tokens out12,758 prompt tokens
Let's run these tests and see if they pass.
TOOL CALL · run_command
{
"command": "pytest tests/series_only/scatter_test.py -q --tb=short --no-header"
}Result of run_command 161 characters
{
"status": "ok",
"stdout": "..................... [100%]\n21 passed in 0.49s\n",
"stderr": "",
"exit_code": 0
}Turn 14at 277 s47 tokens out12,869 prompt tokens
All passed. Wait, let's check if there are tests for duplicate indices in there.
TOOL CALL · read_file
{
"filepath": "tests/series_only/scatter_test.py"
}Result of read_file 2,425 characters
{
"status": "ok",
"filepath": "tests/series_only/scatter_test.py",
"content": "from __future__ import annotations\n\nimport pandas as pd\n\nimport narwhals as nw\nfrom tests.utils import ConstructorEager, assert_equal_data\n\n\ndef test_scatter(constructor_eager: ConstructorEager) -> None:\n df = nw.from_native(\n constructor_eager({\"a\": [1, 2, 3], \"b\": [142, 124, 132]}), eager_only=True\n )\n result = df.with_columns(\n df[\"a\"].scatter([0, 1], [999, 888]), df[\"b\"].scatter([0, 2, 1], df[\"b\"])\n )\n expected = {\"a\": [999, 888, 3], \"b\": [142, 132, 124]}\n assert_equal_data(result, expected)\n\n\ndef test_scatter_indices() -> None:\n s = nw.from_native(pd.Series([2, 3, 6], index=[1, 0, 2]), series_only=True)\n result = s.scatter([1, 0, 2], s)\n expected = pd.Series([3, 2, 6], index=[1, 0, 2])\n pd.testing.assert_series_equal(result.to_native(), expected)\n\n\ndef test_scatter_unchanged(constructor_eager: ConstructorEager) -> None:\n df = nw.from_native(\n constructor_eager({\"a\": [1, 2, 3], \"b\": [142, 124, 132]}), eager_only=True\n )\n df.with_columns(\n df[\"a\"].scatter([0, 1], [999, 888]), df[\"b\"].scatter([0, 2, 1], [142, 124, 132])\n )\n expected = {\"a\": [1, 2, 3], \"b\": [142, 124, 132]}\n assert_equal_data(df, expected)\n\n\ndef test_single_series(constructor_eager: ConstructorEager) -> None:\n df = nw.from_native(\n constructor_eager({\"a\": [1, 2, 3], \"b\": [142, 124, 132]}), eager_only=True\n )\n s = df[\"a\"]\n s.scatter([0, 1], [999, 888])\n expected = {\"a\": [1, 2, 3]}\n assert_equal_data({\"a\": s}, expected)\n\n\ndef test_scatter_integer(constructor_eager: ConstructorEager) -> None:\n df = nw.from_native(\n constructor_eager({\"a\": [1, 2, 3], \"b\": [142, 124, 132]}), eager_only=True\n )\n s = df[\"a\"]\n result = s.scatter(0, 999)\n expected = {\"a\": [999, 2, 3]}\n assert_equal_data({\"a\": result}, expected)\n\n\ndef test_scatter_unordered_indices(constructor_eager: ConstructorEager) -> None:\n data = {\"a\": [16, 12, 10, 9, 6, 5, 2]}\n indices = [6, 1, 0, 5, 3, 2, 4]\n df = nw.from_native(constructor_eager(data))\n result = df[\"a\"].scatter(indices, df[\"a\"])\n assert_equal_data({\"a\": result}, {\"a\": [10, 12, 5, 6, 2, 9, 16]})",
"start_line": 1,
"end_line": 63,
"total_lines": 63,
"is_truncated": false
}Turn 15at 311 s546 tokens out13,975 prompt tokens
No duplicate indices in the tests.
Let's check the return type.
`pc_replace_with_mask` returns a `ChunkedArray` or `Array`.
`self._with_native(...)` wraps it back into a `Narwhals Series`.
The return type of `scatter` is `Self`, so this is correct.
One last thing: does `indices` being a `Sequence[int]` always work with `pa.array(indices)`? Yes, PyArrow supports lists of integers.
Does `values` being `self.__class__` always work?
```python
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
```
`values.native` is a `ChunkedArray` (or `Array`). `combine_chunks()` returns a single `Array`.
`pc.replace_with_mask` accepts `ChunkedArray` as the first arg and `Array` for the replacements.
Wait, if `values` is a `Series`, `values_native` becomes `values.native.combine_chunks()`.
If `values` is a list, `values_native = pa.array(values)`.
The `sorting_indices` is applied to both:
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
`indices_native.take()` returns a `ChunkedArray`.
`values_native.take()` returns a `ChunkedArray` or `Array`.
PyArrow's `pc.replace_with_mask` handles `ChunkedArray` for `replacements` too? Let's check.
TOOL CALL · run_command
{
"command": "python3 - <<'PY'\nimport pyarrow as pa\nimport pyarrow.compute as pc\nimport numpy as np\n\narr = pa.array([1, 2, 3])\nmask = np.array([True, False, True])\n# Create a ChunkedArray for replacements\nreplacements = pa.chunked_array([pa.array([999]), pa.array([888])])\n\ntry:\n res = pc.replace_with_mask(arr, mask, replacements)\n print(\"Result:\", res)\nexcept Exception as e:\n print(\"Error:\", e)\nPY\n"
}Result of run_command 168 characters
{
"status": "ok",
"stdout": "Error: Replacements must be array or scalar, not ChunkedArray([\n [\n 999\n ],\n [\n 888\n ]\n])\n",
"stderr": "",
"exit_code": 0
}Turn 16at 368 s1,018 tokens out14,602 prompt tokens
Aha! So `replacements` MUST be an `Array`, not a `ChunkedArray`.
In `narwhals/_arrow/series.py`:
```python
if isinstance(indices, int):
indices_native = pa.array([indices])
values_native = pa.array([values])
else:
indices_native = pa.array(indices)
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
else:
pa_array: Incomplete = pa.array
values_native = pa_array(values)
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
`pa.array(indices)` returns an `Array` (or `ChunkedArray` if it's large, but usually `Array`).
Actually, `pa.array` usually returns an `ArrowArray` (which is an `Array`). `pa.chunked_array` returns `ChunkedArray`.
Wait, let's check what `pa.array` returns.
And more importantly, what `.take()` returns.
According to pyarrow docs, `Array.take()` returns an `Array`. `ChunkedArray.take()` returns a `ChunkedArray`.
If `indices_native` is a `ChunkedArray`, `values_native.take(sorting_indices)` will return a `ChunkedArray`.
This might be the reason for the error if the input was large enough to be chunked.
But for most small examples, it's an `Array`.
Wait, if `values` is a `Series`, `values_native = values.native.combine_chunks()`. This returns an `Array`.
Then `values_native.take(sorting_indices)` returns an `Array` if `values_native` is an `Array`.
If `values` is a list, `values_native = pa.array(values)`, which is an `Array`.
Then `values_native.take(sorting_indices)` returns an `Array`.
So as long as `values_native` is an `Array` before `.take()`, it should be fine.
Is it possible `pa.array(values)` returns a `ChunkedArray`? No, `pa.array` returns `pa.Array`. `pa.chunked_array` returns `pa.ChunkedArray`.
So `values_native` should always be an `Array`.
Let's double check if `indices_native.take()` could be problematic.
`indices_native = pa.array(indices)`. This is an `Array`.
`indices_native.take(sorting_indices)`. This is an `Array`.
Wait, what about `self.native`?
`self.native` is the native representation of the series, which in `ArrowSeries` is often a `ChunkedArray`.
`pc.replace_with_mask(self.native, mask, values_native)`
`self.native` is `ChunkedArray`. `mask` is `np.ndarray`. `values_native` is `Array`.
This works.
Let's check if there's any case where `values_native` could be a `ChunkedArray`.
If `values` is a `Series`, `values_native = values.native.combine_chunks()`. This explicitly makes it an `Array`.
If `values` is not a `Series`, `values_native = pa.array(values)`. This is an `Array`.
So `values_native` is always an `Array` before `.take()`.
And `Array.take()` returns an `Array`.
So it should be fine.
I'll do one more check to make sure no other `scatter` implementations are broken.
`narwhals/_polars/series.py` uses `.scatter()` from Polars.
`narwhals/_pandas_like/series.py` uses `.iloc[indices] = values`.
These should be fine.
Final check of the code change.
```python
- pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
+ pc_replace_with_mask(self.native, mask, values_native)
```
Yes, this is correct.
I'll check the `git diff` and submit.
TOOL CALL · run_command
{
"command": "git status --short && git diff"
}Result of run_command 677 characters
{
"status": "ok",
"stdout": " M narwhals/_arrow/series.py\ndiff --git a/narwhals/_arrow/series.py b/narwhals/_arrow/series.py\nindex e22d20f..a846e50 100644\n--- a/narwhals/_arrow/series.py\n+++ b/narwhals/_arrow/series.py\n@@ -468,7 +468,7 @@ class ArrowSeries(EagerSeries[\"ChunkedArrayAny\"]):\n # - Missing return type\n pc_replace_with_mask: Incomplete = pc.replace_with_mask\n return self._with_native(\n- pc_replace_with_mask(self.native, mask, values_native.take(indices_native))\n+ pc_replace_with_mask(self.native, mask, values_native)\n )\n \n def to_list(self) -> list[Any]:\n",
"stderr": "",
"exit_code": 0
}Turn 17at 430 s16 tokens out5,437 prompt tokens
The diff is clean.
TOOL CALL · submit_patch
Result of submit_patch 55 characters
{
"status": "ok",
"patch_size": 572,
"files_changed": 1
}Turn 18at 439 s122 tokens out5,492 prompt tokens
OK. I've fixed the bug and verified it.
Turn 19at 439 s
The `ArrowSeries.scatter` method in the `pyarrow` backend was incorrectly calling `.take(indices_native)` on the replacement values, which led to `Index out of bounds` errors when the provided indices did not cover the full length of the original series. This call was redundant and erroneous since the positions of the replacement values are already determined by the boolean mask passed to `pc.replace_with_mask`. The fix removes this `.take()` call, ensuring the replacement values are correctly applied to the masked positions.
Model calls (not matched to turns)
Generated tokens 335 tokens · stopped: STOP
The user is reporting a bug in `ArrowSeries.scatter` where it raises an "out of bound" error when `indices` is not 0 or not the full length of the series.
Looking at the provided repro:
```python
import narwhals as nw
import pyarrow as pa
tbl = pa.table({"a": [1, 2, 3], "b": [142, 124, 132]})
frame = nw.from_native(tbl, eager_only=True)
ser = frame["a"]
try:
result = ser.scatter(1, 999)
except Exception as exc:
print(exc)
try:
result = ser.scatter([0, 2], [999, 888])
except Exception as exc:
print(exc)
```
The output is:
`Index 1 out of bounds`
`Index 2 out of bounds`
This looks like it's coming from the pyarrow backend implementation of `scatter`.
I need to find where `scatter` is implemented for `ArrowSeries`.
Based on the workspace layout:
`./narwhals/_arrow/series.py` seems like the most likely place.
Let's start by searching for `scatter` in `narwhals/_arrow/series.py`.<|channel>thought
The user is reporting a bug in `ArrowSeries.scatter` where it raises an "out of bound" error when `indices` is not 0 or not the full length of the series.
Looking at the provided repro:
```python
import narwhals as nw
import pyarrow as pa
tbl = pa.table({"a": [1, 2, 3], "b": [142, 124, 132]})
frame = nw.from_native(tbl, eager_only=True)
ser = frame["a"]
try:
result = ser.scatter(1, 999)
except Exception as exc:
print(exc)
try:
result = ser.scatter([0, 2], [999, 888])
except Exception as exc:
print(exc)
```
The output is:
`Index 1 out of bounds`
`Index 2 out of bounds`
This looks like it's coming from the pyarrow backend implementation of `scatter`.
I need to find where `scatter` is implemented for `ArrowSeries`.
Based on the workspace layout:
`./narwhals/_arrow/series.py` seems like the most likely place.
Let's start by searching for `scatter` in `narwhals/_arrow/series.py`.<channel|><|tool_call>call:run_command{command:<|"|>grep -rn --include="*.py" "def scatter" narwhals/<|"|>}<tool_call|><|tool_response>
Generated tokens 100 tokens · stopped: STOP
Okay, I see `scatter` implemented in several places. The report specifically mentions pyarrow backed series, so `narwhals/_arrow/series.py` is the target. Let's examine the implementation of `scatter` in `narwhals/_arrow/series.py`.
Okay, I see `scatter` implemented in several places. The report specifically mentions pyarrow backed series, so `narwhals/_arrow/series.py` is the target.
Let's examine the implementation of `scatter` in `narwhals/_arrow/series.py`.<channel|><|tool_call>call:read_file{filepath:<|"|>narwhals/_arrow/series.py<|"|>,start_line:400,end_line:470}<tool_call|><|tool_response>
Generated tokens 86 tokens · stopped: STOP
Wait, the `read_file` output is truncated? No, it says `is_truncated: false`, but the code ends with `return self._with_native(`. Let me read more of `scatter`.
Wait, the `read_file` output is truncated? No, it says `is_truncated: false`, but the code ends with `return self._with_native(`.
Let me read more of `scatter`.
<channel|><|tool_call>call:read_file{end_line:480,filepath:<|"|>narwhals/_arrow/series.py<|"|>,start_line:460}<tool_call|><|tool_response>
Generated tokens 1,003 tokens · stopped: STOP
Wait, look at this line:
`return self._with_native(pc_replace_with_mask(self.native, mask, values_native.take(indices_native)))`
`indices_native` are the indices we want to replace.
`values_native` are the new values.
`mask` is a boolean array of the same size as `self.native`, where it's `True` at `indices_native`.
The problem is `values_native.take(indices_native)`.
If `indices_native` are `[1]`, and `values_native` is `[999]`, then `values_native.take(indices_native)` will try to take the element at index 1 from `values_native`, which only has one element at index 0. This is why it's raising "out of bound error".
`values_native` should already be the values to put at `indices_native`.
Let's re-examine:
```python
if isinstance(indices, int):
indices_native = pa.array([indices])
values_native = pa.array([values])
else:
# TODO(unassigned): we may also want to let `indices` be a Series.
# https://github.com/narwhals-dev/narwhals/issues/2155
indices_native = pa.array(indices)
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
else:
# NOTE: Requires fixes in https://github.com/zen-xu/pyarrow-stubs/pull/209
pa_array: Incomplete = pa.array
values_native = pa_array(values)
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
Here `indices_native` and `values_native` are aligned.
Then:
```python
mask: _1DArray = np.zeros(self.len(), dtype=bool)
mask[indices_native] = True
# ...
return self._with_native(
pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
)
```
The `pc.replace_with_mask` takes:
1. The original array.
2. A boolean mask (where to replace).
3. The replacements.
According to pyarrow's `replace_with_mask` (or rather `pc.replace_with_mask` wrapper if it exists, though it might be `pc.replace_with_mask` in newer versions of pyarrow, or something else), the third argument should be the array of replacements.
If we have:
`self.native` = `[1, 2, 3]`
`indices` = `[0, 2]`
`values` = `[999, 888]`
`mask` = `[True, False, True]`
`values_native` = `[999, 888]`
`values_native.take(indices_native)` will try to do `[999, 888].take([0, 2])`, which fails because index 2 is out of bounds for `[999, 888]`.
It should just be `values_native`.
Let's verify this by running the repro.
Wait, look at this line:
`return self._with_native(pc_replace_with_mask(self.native, mask, values_native.take(indices_native)))`
`indices_native` are the indices we want to replace.
`values_native` are the new values.
`mask` is a boolean array of the same size as `self.native`, where it's `True` at `indices_native`.
The problem is `values_native.take(indices_native)`.
If `indices_native` are `[1]`, and `values_native` is `[999]`, then `values_native.take(indices_native)` will try to take the element at index 1 from `values_native`, which only has one element at index 0. This is why it's raising "out of bound error".
`values_native` should already be the values to put at `indices_native`.
Let's re-examine:
```python
if isinstance(indices, int):
indices_native = pa.array([indices])
values_native = pa.array([values])
else:
# TODO(unassigned): we may also want to let `indices` be a Series.
# https://github.com/narwhals-dev/narwhals/issues/2155
indices_native = pa.array(indices)
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
else:
# NOTE: Requires fixes in https://github.com/zen-xu/pyarrow-stubs/pull/209
pa_array: Incomplete = pa.array
values_native = pa_array(values)
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
Here `indices_native` and `values_native` are aligned.
Then:
```python
mask: _1DArray = np.zeros(self.len(), dtype=bool)
mask[indices_native] = True
# ...
return self._with_native(
pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
)
```
The `pc.replace_with_mask` takes:
1. The original array.
2. A boolean mask (where to replace).
3. The replacements.
According to pyarrow's `replace_with_mask` (or rather `pc.replace_with_mask` wrapper if it exists, though it might be `pc.replace_with_mask` in newer versions of pyarrow, or something else), the third argument should be the array of replacements.
If we have:
`self.native` = `[1, 2, 3]`
`indices` = `[0, 2]`
`values` = `[999, 888]`
`mask` = `[True, False, True]`
`values_native` = `[999, 888]`
`values_native.take(indices_native)` will try to do `[999, 888].take([0, 2])`, which fails because index 2 is out of bounds for `[999, 888]`.
It should just be `values_native`.
Let's verify this by running the repro.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import narwhals as nw
import pyarrow as pa
tbl = pa.table({"a": [1, 2, 3], "b": [142, 124, 132]})
frame = nw.from_native(tbl, eager_only=True)
ser = frame["a"]
try:
result = ser.scatter(1, 999)
print("Success 1:", result)
except Exception as exc:
print("Error 1:", exc)
try:
result = ser.scatter([0, 2], [999, 888])
print("Success 2:", result)
except Exception as exc:
print("Error 2:", exc)
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 304 tokens · stopped: STOP
Exactly as reported. The fix should be to remove `.take(indices_native)` from the last line. Wait, let me check the documentation for `pc.replace_with_mask` if possible, or just deduce it. If `mask` has `N` True values, then the replacements array should probably have `N` values? Or should it be the same length as the original array? Actually, in PyArrow's `compute.replace_with_mask`, the `replacements` array must be the same length as the original array? No, that's usually not how it works for masks. Wait, I should check how `pc.replace_with_mask` works in pyarrow. Since I don't have internet, I'll test it in a small script.
Exactly as reported.
The fix should be to remove `.take(indices_native)` from the last line.
Wait, let me check the documentation for `pc.replace_with_mask` if possible, or just deduce it.
If `mask` has `N` True values, then the replacements array should probably have `N` values? Or should it be the same length as the original array?
Actually, in PyArrow's `compute.replace_with_mask`, the `replacements` array must be the same length as the original array? No, that's usually not how it works for masks.
Wait, I should check how `pc.replace_with_mask` works in pyarrow.
Since I don't have internet, I'll test it in a small script.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import pyarrow as pa
import pyarrow.compute as pc
import numpy as np
arr = pa.array([1, 2, 3])
mask = np.array([True, False, True])
replacements = pa.array([999, 888])
try:
res = pc.replace_with_mask(arr, mask, replacements)
print("Result:", res)
except Exception as e:
print("Error:", e)
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 445 tokens · stopped: STOP
Yes, `replacements` should be an array containing only the values for the `True` positions in the mask, in the order they appear in the original array.
In the `scatter` implementation:
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
This part ensures that `indices_native` are sorted and `values_native` are sorted accordingly.
Then `mask` is created:
```python
mask: _1DArray = np.zeros(self.len(), dtype=bool)
mask[indices_native] = True
```
So `indices_native` tells us where the True valeurs are in `mask`, in increasing order.
And `values_native` contains the replacement values for those indices, also in increasing order of index.
So `pc_replace_with_mask(self.native, mask, values_native)` is exactly what is needed.
Let's check if there are any other parallel implementations of `scatter` that might need similar fixes.
I saw:
- `narwhals/_compliant/series.py`
- `narwhals/series.py`
- `narwhals/_pandas_like/series.py`
- `narwhals/_polars/series.py`
But `narwhals/series.py` is likely the public API that delegates to the backend.
`narwhals/_compliant/series.py` is probably for compliance tests.
`narwhals/_pandas_like/series.py` might be a common base or similar.
`narwhals/_polars/series.py` is the Polars backend.
Let's check `narwhals/series.py`.
Yes, `replacements` should be an array containing only the values for the `True` positions in the mask, in the order they appear in the original array.
In the `scatter` implementation:
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
This part ensures that `indices_native` are sorted and `values_native` are sorted accordingly.
Then `mask` is created:
```python
mask: _1DArray = np.zeros(self.len(), dtype=bool)
mask[indices_native] = True
```
So `indices_native` tells us where the True valeurs are in `mask`, in increasing order.
And `values_native` contains the replacement values for those indices, also in increasing order of index.
So `pc_replace_with_mask(self.native, mask, values_native)` is exactly what is needed.
Let's check if there are any other parallel implementations of `scatter` that might need similar fixes.
I saw:
- `narwhals/_compliant/series.py`
- `narwhals/series.py`
- `narwhals/_pandas_like/series.py`
- `narwhals/_polars/series.py`
But `narwhals/series.py` is likely the public API that delegates to the backend.
`narwhals/_compliant/series.py` is probably for compliance tests.
`narwhals/_pandas_like/series.py` might be a common base or similar.
`narwhals/_polars/series.py` is the Polars backend.
Let's check `narwhals/series.py`.
<channel|><|tool_call>call:read_file{end_line:250,filepath:<|"|>narwhals/series.py<|"|>,start_line:220}<tool_call|><|tool_response>
Generated tokens 152 tokens · stopped: STOP
`narwhals/series.py` just defines the interface and presumably delegates. Let's see how it does that. Wait, the layout says `narwhals/series.py` is the main Series class. But I don't see how it calls the backend in the snippet. Wait, `narwhals` usually works by translating high-level calls to backend-specific calls. Let's check `narwhals/_polars/series.py` to see if it has a similar bug.
`narwhals/series.py` just defines the interface and presumably delegates. Let's see how it does that.
Wait, the layout says `narwhals/series.py` is the main Series class. But I don't see how it calls the backend in the snippet.
Wait, `narwhals` usually works by translating high-level calls to backend-specific calls.
Let's check `narwhals/_polars/series.py` to see if it has a similar bug.
<channel|><|tool_call>call:read_file{end_line:450,filepath:<|"|>narwhals/_polars/series.py<|"|>,start_line:420}<tool_call|><|tool_response>
Generated tokens 75 tokens · stopped: STOP
Polars implementation is very different and leverages Polars' own `scatter`. What about `narwhals/_pandas_like/series.py`?
Polars implementation is very different and leverages Polars' own `scatter`.
What about `narwhals/_pandas_like/series.py`?
<channel|><|tool_call>call:read_file{end_line:300,filepath:<|"|>narwhals/_pandas_like/series.py<|"|>,start_line:260}<tool_call|><|tool_response>
Generated tokens 149 tokens · stopped: STOP
This looks like a pandas-like implementation. The bug was specifically for `ArrowSeries`, which is implemented in `narwhals/_arrow/series.py`. Let's apply the fix.
This looks like a pandas-like implementation.
The bug was specifically for `ArrowSeries`, which is implemented in `narwhals/_arrow/series.py`.
Let's apply the fix.
<channel|><|tool_call>call:edit_file{filepath:<|"|>narwhals/_arrow/series.py<|"|>,new_string:<|"|> return self._with_native(
pc_replace_with_mask(self.native, mask, values_native)
)<|"|>,old_string:<|"|> return self._with_native(
pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
)<|"|>}<tool_call|><|tool_response>
Generated tokens 206 tokens · stopped: STOP
Now let's verify with the repro script again.
Now let's verify with the repro script again.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import narwhals as nw
import pyarrow as pa
tbl = pa.table({"a": [1, 2, 3], "b": [142, 124, 132]})
frame = nw.from_native(tbl, eager_only=True)
ser = frame["a"]
try:
result = ser.scatter(1, 999)
print("Success 1:", result)
except Exception as exc:
print("Error 1:", exc)
try:
result = ser.scatter([0, 2], [999, 888])
print("Success 2:", result)
except Exception as exc:
print("Error 2:", exc)
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 663 tokens · stopped: STOP
The repro is fixed. Now I should check if there are any other cases to consider.
The indices can be a single integer or a sequence of integers.
What if indices are not sorted?
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
This part handles unsorted indices by sorting both `indices_native` and `values_native` so they align with the mask (which is indexed by `indices_native`).
Wait, let's trace it:
If `indices = [2, 0]` and `values = [888, 999]`
`indices_native` = `[2, 0]`
`values_native` = `[888, 999]`
`sorting_indices` = `[1, 0]` (because `indices_native[1]=0` and `indices_native[0]=2`)
`indices_native` becomes `[0, 2]`
`values_native` becomes `[999, 888]`
Then `mask` becomes `[True, False, True]`
`pc_replace_with_mask(self.native, mask, [999, 888])` will put 999 at index 0 and 888 at index 2. Correct.
What if there are duplicate indices?
`indices = [0, 0]` and `values = [888, 999]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`sorting_indices` = `[0, 1]` or `[1, 0]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`mask` = `[True, False, False]`
`pc_replace_with_mask(self.native, mask, [888, 999])` -> This might actually fail in PyArrow if the replacements array is longer than the number of True values in the mask.
Let's check PyArrow's `pc.replace_with_mask` with duplicate indices.
The repro is fixed. Now I should check if there are any other cases to consider.
The indices can be a single integer or a sequence of integers.
What if indices are not sorted?
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
This part handles unsorted indices by sorting both `indices_native` and `values_native` so they align with the mask (which is indexed by `indices_native`).
Wait, let's trace it:
If `indices = [2, 0]` and `values = [888, 999]`
`indices_native` = `[2, 0]`
`values_native` = `[888, 999]`
`sorting_indices` = `[1, 0]` (because `indices_native[1]=0` and `indices_native[0]=2`)
`indices_native` becomes `[0, 2]`
`values_native` becomes `[999, 888]`
Then `mask` becomes `[True, False, True]`
`pc_replace_with_mask(self.native, mask, [999, 888])` will put 999 at index 0 and 888 at index 2. Correct.
What if there are duplicate indices?
`indices = [0, 0]` and `values = [888, 999]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`sorting_indices` = `[0, 1]` or `[1, 0]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`mask` = `[True, False, False]`
`pc_replace_with_mask(self.native, mask, [888, 999])` -> This might actually fail in PyArrow if the replacements array is longer than the number of True values in the mask.
Let's check PyArrow's `pc.replace_with_mask` with duplicate indices.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import pyarrow as pa
import pyarrow.compute as pc
import numpy as np
arr = pa.array([1, 2, 3])
mask = np.array([True, False, False])
replacements = pa.array([888, 999])
try:
res = pc.replace_with_mask(arr, mask, replacements)
print("Result:", res)
except Exception as e:
print("Error:", e)
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 666 tokens · stopped: STOP
It seems PyArrow just uses the first few elements of `replacements` that match the number of `True` values. Wait, wait. Let's re-read the output: `Result: [888, 2, 3]`. It used 888 at index 0. What if I change the mask to have two True? `mask = np.array([True, True, False])` `replacements = pa.array([888, 999])` Result: `[888, 999, 3]`. So if we have duplicate indices, `mask[indices_native] = True` will only set that position to True once. The `values_native` array will have as many elements as `indices`. If `indices` has duplicates, `len(values_native)` will be greater than `mask.sum()`. The `scatter` behavior in pandas (which narwhals mimics) is that for duplicate indices, the last value wins. Let's see what happens with our current implementation when there are duplicate indices. `indices = [0, 0]`, `values = [888, 999]` `indices_native` = `[0, 0]` `values_native` = `[888, 999]` `sorting_indices` = `[0, 1]` `indices_native` = `[0, 0]` `values_native` = `[888, 999]` `mask` = `[True, False, False]` `pc_replace_with_mask(self.native, mask, [888, 999])` -> Result `[888, 2, 3]`. But it should be `[999, 2, 3]` because the last value for index 0 is 999. Does this matter? The issue description didn't mention duplicate indices, so maybe it's out of scope, but a "principal engineer" would check this. Actually, looking at the current implementation of `scatter` in `_arrow/series.py`, it uses `pc.replace_with_mask`. If we want "last value wins", we might need to avoid duplicates in `indices_native` and only keep the last corresponding value in `values_native`. However, let's check if other backends (like Polars) handle this. Polars `scatter` also handles duplicate indices. Wait, if I'm supposed to provide a MINIMAL root-cause patch, maybe I should just fix the bug reported. The reported bug is: `ArrowSeries.scatter` raises out of bound error when `indices` is not 0 or not full length. The fix I applied addresses this exactly. Let's double check if any existing tests cover `scatter`.
It seems PyArrow just uses the first few elements of `replacements` that match the number of `True` values.
Wait, wait. Let's re-read the output: `Result: [888, 2, 3]`.
It used 888 at index 0.
What if I change the mask to have two True?
`mask = np.array([True, True, False])`
`replacements = pa.array([888, 999])`
Result: `[888, 999, 3]`.
So if we have duplicate indices, `mask[indices_native] = True` will only set that position to True once.
The `values_native` array will have as many elements as `indices`.
If `indices` has duplicates, `len(values_native)` will be greater than `mask.sum()`.
The `scatter` behavior in pandas (which narwhals mimics) is that for duplicate indices, the last value wins.
Let's see what happens with our current implementation when there are duplicate indices.
`indices = [0, 0]`, `values = [888, 999]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`sorting_indices` = `[0, 1]`
`indices_native` = `[0, 0]`
`values_native` = `[888, 999]`
`mask` = `[True, False, False]`
`pc_replace_with_mask(self.native, mask, [888, 999])` -> Result `[888, 2, 3]`.
But it should be `[999, 2, 3]` because the last value for index 0 is 999.
Does this matter? The issue description didn't mention duplicate indices, so maybe it's out of scope, but a "principal engineer" would check this.
Actually, looking at the current implementation of `scatter` in `_arrow/series.py`, it uses `pc.replace_with_mask`.
If we want "last value wins", we might need to avoid duplicates in `indices_native` and only keep the last corresponding value in `values_native`.
However, let's check if other backends (like Polars) handle this.
Polars `scatter` also handles duplicate indices.
Wait, if I'm supposed to provide a MINIMAL root-cause patch, maybe I should just fix the bug reported.
The reported bug is: `ArrowSeries.scatter` raises out of bound error when `indices` is not 0 or not full length.
The fix I applied addresses this exactly.
Let's double check if any existing tests cover `scatter`.
<channel|><|tool_call>call:run_command{command:<|"|>grep -rn "test_scatter" tests/<|"|>}<tool_call|><|tool_response>
Generated tokens 50 tokens · stopped: STOP
Let's run these tests and see if they pass.
Let's run these tests and see if they pass.
<channel|><|tool_call>call:run_command{command:<|"|>pytest tests/series_only/scatter_test.py -q --tb=short --no-header<|"|>}<tool_call|><|tool_response>
Generated tokens 47 tokens · stopped: STOP
All passed. Wait, let's check if there are tests for duplicate indices in there.
All passed.
Wait, let's check if there are tests for duplicate indices in there.
<channel|><|tool_call>call:read_file{filepath:<|"|>tests/series_only/scatter_test.py<|"|>}<tool_call|><|tool_response>
Generated tokens 546 tokens · stopped: STOP
No duplicate indices in the tests.
Let's check the return type.
`pc_replace_with_mask` returns a `ChunkedArray` or `Array`.
`self._with_native(...)` wraps it back into a `Narwhals Series`.
The return type of `scatter` is `Self`, so this is correct.
One last thing: does `indices` being a `Sequence[int]` always work with `pa.array(indices)`? Yes, PyArrow supports lists of integers.
Does `values` being `self.__class__` always work?
```python
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
```
`values.native` is a `ChunkedArray` (or `Array`). `combine_chunks()` returns a single `Array`.
`pc.replace_with_mask` accepts `ChunkedArray` as the first arg and `Array` for the replacements.
Wait, if `values` is a `Series`, `values_native` becomes `values.native.combine_chunks()`.
If `values` is a list, `values_native = pa.array(values)`.
The `sorting_indices` is applied to both:
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
`indices_native.take()` returns a `ChunkedArray`.
`values_native.take()` returns a `ChunkedArray` or `Array`.
PyArrow's `pc.replace_with_mask` handles `ChunkedArray` for `replacements` too? Let's check.
No duplicate indices in the tests.
Let's check the return type.
`pc_replace_with_mask` returns a `ChunkedArray` or `Array`.
`self._with_native(...)` wraps it back into a `Narwhals Series`.
The return type of `scatter` is `Self`, so this is correct.
One last thing: does `indices` being a `Sequence[int]` always work with `pa.array(indices)`? Yes, PyArrow supports lists of integers.
Does `values` being `self.__class__` always work?
```python
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
```
`values.native` is a `ChunkedArray` (or `Array`). `combine_chunks()` returns a single `Array`.
`pc.replace_with_mask` accepts `ChunkedArray` as the first arg and `Array` for the replacements.
Wait, if `values` is a `Series`, `values_native` becomes `values.native.combine_chunks()`.
If `values` is a list, `values_native = pa.array(values)`.
The `sorting_indices` is applied to both:
```python
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
`indices_native.take()` returns a `ChunkedArray`.
`values_native.take()` returns a `ChunkedArray` or `Array`.
PyArrow's `pc.replace_with_mask` handles `ChunkedArray` for `replacements` too? Let's check.
<channel|><|tool_call>call:run_command{command:<|"|>python3 - <<'PY'
import pyarrow as pa
import pyarrow.compute as pc
import numpy as np
arr = pa.array([1, 2, 3])
mask = np.array([True, False, True])
# Create a ChunkedArray for replacements
replacements = pa.chunked_array([pa.array([999]), pa.array([888])])
try:
res = pc.replace_with_mask(arr, mask, replacements)
print("Result:", res)
except Exception as e:
print("Error:", e)
PY
<|"|>}<tool_call|><|tool_response>
Generated tokens 1,018 tokens · stopped: STOP
Aha! So `replacements` MUST be an `Array`, not a `ChunkedArray`.
In `narwhals/_arrow/series.py`:
```python
if isinstance(indices, int):
indices_native = pa.array([indices])
values_native = pa.array([values])
else:
indices_native = pa.array(indices)
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
else:
pa_array: Incomplete = pa.array
values_native = pa_array(values)
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
`pa.array(indices)` returns an `Array` (or `ChunkedArray` if it's large, but usually `Array`).
Actually, `pa.array` usually returns an `ArrowArray` (which is an `Array`). `pa.chunked_array` returns `ChunkedArray`.
Wait, let's check what `pa.array` returns.
And more importantly, what `.take()` returns.
According to pyarrow docs, `Array.take()` returns an `Array`. `ChunkedArray.take()` returns a `ChunkedArray`.
If `indices_native` is a `ChunkedArray`, `values_native.take(sorting_indices)` will return a `ChunkedArray`.
This might be the reason for the error if the input was large enough to be chunked.
But for most small examples, it's an `Array`.
Wait, if `values` is a `Series`, `values_native = values.native.combine_chunks()`. This returns an `Array`.
Then `values_native.take(sorting_indices)` returns an `Array` if `values_native` is an `Array`.
If `values` is a list, `values_native = pa.array(values)`, which is an `Array`.
Then `values_native.take(sorting_indices)` returns an `Array`.
So as long as `values_native` is an `Array` before `.take()`, it should be fine.
Is it possible `pa.array(values)` returns a `ChunkedArray`? No, `pa.array` returns `pa.Array`. `pa.chunked_array` returns `pa.ChunkedArray`.
So `values_native` should always be an `Array`.
Let's double check if `indices_native.take()` could be problematic.
`indices_native = pa.array(indices)`. This is an `Array`.
`indices_native.take(sorting_indices)`. This is an `Array`.
Wait, what about `self.native`?
`self.native` is the native representation of the series, which in `ArrowSeries` is often a `ChunkedArray`.
`pc.replace_with_mask(self.native, mask, values_native)`
`self.native` is `ChunkedArray`. `mask` is `np.ndarray`. `values_native` is `Array`.
This works.
Let's check if there's any case where `values_native` could be a `ChunkedArray`.
If `values` is a `Series`, `values_native = values.native.combine_chunks()`. This explicitly makes it an `Array`.
If `values` is not a `Series`, `values_native = pa.array(values)`. This is an `Array`.
So `values_native` is always an `Array` before `.take()`.
And `Array.take()` returns an `Array`.
So it should be fine.
I'll do one more check to make sure no other `scatter` implementations are broken.
`narwhals/_polars/series.py` uses `.scatter()` from Polars.
`narwhals/_pandas_like/series.py` uses `.iloc[indices] = values`.
These should be fine.
Final check of the code change.
```python
- pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
+ pc_replace_with_mask(self.native, mask, values_native)
```
Yes, this is correct.
I'll check the `git diff` and submit.Aha! So `replacements` MUST be an `Array`, not a `ChunkedArray`.
In `narwhals/_arrow/series.py`:
```python
if isinstance(indices, int):
indices_native = pa.array([indices])
values_native = pa.array([values])
else:
indices_native = pa.array(indices)
if isinstance(values, self.__class__):
values_native = values.native.combine_chunks()
else:
pa_array: Incomplete = pa.array
values_native = pa_array(values)
sorting_indices = pc.sort_indices(indices_native)
indices_native = indices_native.take(sorting_indices)
values_native = values_native.take(sorting_indices)
```
`pa.array(indices)` returns an `Array` (or `ChunkedArray` if it's large, but usually `Array`).
Actually, `pa.array` usually returns an `ArrowArray` (which is an `Array`). `pa.chunked_array` returns `ChunkedArray`.
Wait, let's check what `pa.array` returns.
And more importantly, what `.take()` returns.
According to pyarrow docs, `Array.take()` returns an `Array`. `ChunkedArray.take()` returns a `ChunkedArray`.
If `indices_native` is a `ChunkedArray`, `values_native.take(sorting_indices)` will return a `ChunkedArray`.
This might be the reason for the error if the input was large enough to be chunked.
But for most small examples, it's an `Array`.
Wait, if `values` is a `Series`, `values_native = values.native.combine_chunks()`. This returns an `Array`.
Then `values_native.take(sorting_indices)` returns an `Array` if `values_native` is an `Array`.
If `values` is a list, `values_native = pa.array(values)`, which is an `Array`.
Then `values_native.take(sorting_indices)` returns an `Array`.
So as long as `values_native` is an `Array` before `.take()`, it should be fine.
Is it possible `pa.array(values)` returns a `ChunkedArray`? No, `pa.array` returns `pa.Array`. `pa.chunked_array` returns `pa.ChunkedArray`.
So `values_native` should always be an `Array`.
Let's double check if `indices_native.take()` could be problematic.
`indices_native = pa.array(indices)`. This is an `Array`.
`indices_native.take(sorting_indices)`. This is an `Array`.
Wait, what about `self.native`?
`self.native` is the native representation of the series, which in `ArrowSeries` is often a `ChunkedArray`.
`pc.replace_with_mask(self.native, mask, values_native)`
`self.native` is `ChunkedArray`. `mask` is `np.ndarray`. `values_native` is `Array`.
This works.
Let's check if there's any case where `values_native` could be a `ChunkedArray`.
If `values` is a `Series`, `values_native = values.native.combine_chunks()`. This explicitly makes it an `Array`.
If `values` is not a `Series`, `values_native = pa.array(values)`. This is an `Array`.
So `values_native` is always an `Array` before `.take()`.
And `Array.take()` returns an `Array`.
So it should be fine.
I'll do one more check to make sure no other `scatter` implementations are broken.
`narwhals/_polars/series.py` uses `.scatter()` from Polars.
`narwhals/_pandas_like/series.py` uses `.iloc[indices] = values`.
These should be fine.
Final check of the code change.
```python
- pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
+ pc_replace_with_mask(self.native, mask, values_native)
```
Yes, this is correct.
I'll check the `git diff` and submit.<channel|><|tool_call>call:run_command{command:<|"|>git status --short && git diff<|"|>}<tool_call|><|tool_response>
Generated tokens 16 tokens · stopped: STOP
The diff is clean.
The diff is clean.
<channel|><|tool_call>call:submit_patch{}<tool_call|><|tool_response>
Patch, tests and logs
Final code change Included
diff --git a/narwhals/_arrow/series.py b/narwhals/_arrow/series.py
index e22d20f..a846e50 100644
--- a/narwhals/_arrow/series.py
+++ b/narwhals/_arrow/series.py
@@ -468,7 +468,7 @@ class ArrowSeries(EagerSeries["ChunkedArrayAny"]):
# - Missing return type
pc_replace_with_mask: Incomplete = pc.replace_with_mask
return self._with_native(
- pc_replace_with_mask(self.native, mask, values_native.take(indices_native))
+ pc_replace_with_mask(self.native, mask, values_native)
)
def to_list(self) -> list[Any]:
Test output Included
============================= test session starts ============================== collected 25 items tests/series_only/scatter_test.py ......................... [100%] ==================================== PASSES ==================================== - generated xml file: /tmp/rebench-grade-463293e96df943cc925f2b4e63d181b5.xml -- =========================== short test summary info ============================ PASSED tests/series_only/scatter_test.py::test_scatter_indices PASSED tests/series_only/scatter_test.py::test_single_series[pyarrow] PASSED tests/series_only/scatter_test.py::test_scatter_unordered_indices[pyarrow] PASSED tests/series_only/scatter_test.py::test_scatter_2862[pandas[pyarrow]] PASSED tests/series_only/scatter_test.py::test_scatter_2862[polars[eager]] PASSED tests/series_only/scatter_test.py::test_single_series[polars[eager]] PASSED tests/series_only/scatter_test.py::test_scatter_unordered_indices[pandas] PASSED tests/series_only/scatter_test.py::test_scatter_integer[pandas[pyarrow]] PASSED tests/series_only/scatter_test.py::test_scatter_2862[pyarrow] PASSED tests/series_only/scatter_test.py::test_scatter_unchanged[polars[eager]] PASSED tests/series_only/scatter_test.py::test_scatter_integer[polars[eager]] PASSED tests/series_only/scatter_test.py::test_single_series[pandas] PASSED tests/series_only/scatter_test.py::test_scatter_unordered_indices[polars[eager]] PASSED tests/series_only/scatter_test.py::test_scatter[pyarrow] PASSED tests/series_only/scatter_test.py::test_scatter_integer[pandas] PASSED tests/series_only/scatter_test.py::test_scatter[polars[eager]] PASSED tests/series_only/scatter_test.py::test_scatter_unchanged[pandas] PASSED tests/series_only/scatter_test.py::test_scatter_unordered_indices[pandas[pyarrow]] PASSED tests/series_only/scatter_test.py::test_scatter_unchanged[pyarrow] PASSED tests/series_only/scatter_test.py::test_scatter_integer[pyarrow] PASSED tests/series_only/scatter_test.py::test_scatter[pandas[pyarrow]] PASSED tests/series_only/scatter_test.py::test_single_series[pandas[pyarrow]] PASSED tests/series_only/scatter_test.py::test_scatter_2862[pandas] PASSED tests/series_only/scatter_test.py::test_scatter[pandas] PASSED tests/series_only/scatter_test.py::test_scatter_unchanged[pandas[pyarrow]] ============================== 25 passed in 0.53s ==============================
Test errors Included
Test report (JUnit) Included
<?xml version="1.0" encoding="utf-8"?><testsuites name="pytest tests"><testsuite name="pytest" errors="0" failures="0" skipped="0" tests="25" time="0.094" timestamp="2026-11-14T04:08:04.647301+00:00" hostname="17ab1a01969a"><testcase classname="tests.series_only.scatter_test" name="test_scatter_indices" time="0.021" /><testcase classname="tests.series_only.scatter_test" name="test_single_series[pyarrow]" time="0.020" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unordered_indices[pyarrow]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_2862[pandas[pyarrow]]" time="0.002" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_2862[polars[eager]]" time="0.010" /><testcase classname="tests.series_only.scatter_test" name="test_single_series[polars[eager]]" time="0.000" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unordered_indices[pandas]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_integer[pandas[pyarrow]]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_2862[pyarrow]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unchanged[polars[eager]]" time="0.002" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_integer[polars[eager]]" time="0.000" /><testcase classname="tests.series_only.scatter_test" name="test_single_series[pandas]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unordered_indices[polars[eager]]" time="0.000" /><testcase classname="tests.series_only.scatter_test" name="test_scatter[pyarrow]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_integer[pandas]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter[polars[eager]]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unchanged[pandas]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unordered_indices[pandas[pyarrow]]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unchanged[pyarrow]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_integer[pyarrow]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter[pandas[pyarrow]]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_single_series[pandas[pyarrow]]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_2862[pandas]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter[pandas]" time="0.001" /><testcase classname="tests.series_only.scatter_test" name="test_scatter_unchanged[pandas[pyarrow]]" time="0.001" /></testsuite></testsuites>
Agent log Included
[ 0.0s] 📋 System Prompt: You are a principal Python software engineer resolving a repository issue in `/workspace`.
[ 0.0s] 🎯 Task Prompt: You are evaluating a software engineering task for repository narwhals-dev/narwhals.
[ 20.5s] 💭 (911 chars) "The user is reporting a bug in `ArrowSeries.scatter` where it raises an "out of bound" error
when `indices` is not 0 or ..."
[ 20.5s] 🔧 run_command grep -rn --include="*.py" "def scatter" narwhals/
[ 20.5s] → narwhals/_compliant/series.py:251: def scatter(self, indices: int | Sequence[int], values: Any) ->
Self: ...
[ 29.1s] 💭 (233 chars) "Okay, I see `scatter` implemented in several places. The report specifically mentions
pyarrow backed series, so `narwhal..."
[ 29.1s] 📖 read_file (narwhals/_arrow/series.py)
[ 29.2s] ✓ {'status': 'ok', 'filepath': 'narwhals/_arrow/series.py', 'content': ' return
maybe_extract_py_scalar(k, _ret…
[ 33.6s] 💭 (161 chars) "Wait, the `read_file` output is truncated? No, it says `is_truncated: false`, but the code
ends with `return self._with_..."
[ 33.6s] 📖 read_file (narwhals/_arrow/series.py)
[ 33.7s] ✓ {'status': 'ok', 'filepath': 'narwhals/_arrow/series.py', 'content': ' values_native =
values_native.take(sorting…
[ 95.9s] 💭 (2620 chars) "Wait, look at this line:
`return self._with_native(pc_replace_with_mask(self.native, mask, values_native.take(indices_na..."
[ 95.9s] 🔧 run_command (21 lines) python3 - <<'PY'
[ 97.0s] → Error 1: Index 1 out of bounds
[ 121.7s] 💭 (637 chars) "Exactly as reported.
The fix should be to remove `.take(indices_native)` from the last line.
Wait, let me check the do..."
[ 121.7s] 🔧 run_command (15 lines) python3 - <<'PY'
[ 122.2s] → Result: [
[ 157.4s] 💭 (1428 chars) "Yes, `replacements` should be an array containing only the values for the `True` positions
in the mask, in the order the..."
[ 157.4s] 📖 read_file (narwhals/series.py)
[ 157.5s] ✓ {'status': 'ok', 'filepath': 'narwhals/series.py', 'content': ' Series of class that user
started with.\n\n …
[ 169.4s] 💭 (393 chars) "`narwhals/series.py` just defines the interface and presumably delegates. Let's see how it
does that.
Wait, the layout ..."
[ 169.4s] 📖 read_file (narwhals/_polars/series.py)
[ 169.5s] ✓ {'status': 'ok', 'filepath': 'narwhals/_polars/series.py', 'content': ' def sort(self, *, descending:
bool, nulls_las…
[ 174.8s] 💭 (123 chars) "Polars implementation is very different and leverages Polars' own `scatter`.
What about `narwhals/_pandas_like/series.p..."
[ 174.8s] 📖 read_file (narwhals/_pandas_like/series.py)
[ 174.8s] ✓ {'status': 'ok', 'filepath': 'narwhals/_pandas_like/series.py', 'content': ' else:\n
msg = (\n…
[ 182.5s] 💭 (165 chars) "This looks like a pandas-like implementation.
The bug was specifically for `ArrowSeries`, which is implemented in `narw..."
[ 182.5s] ✏️ edit_file (narwhals/_arrow/series.py)
[ 182.7s] ✓ {'status': 'ok', 'filepath': 'narwhals/_arrow/series.py', 'occurrences': 1, 'strategy': 'exact', 'diff':
'--- a/narwhals…
[ 189.7s] 💭 (45 chars) "Now let's verify with the repro script again."
[ 189.7s] 🔧 run_command (21 lines) python3 - <<'PY'
[ 190.1s] → Success 1: ┌───────────────────────────────────────────────────┐
[ 226.6s] 💭 (1480 chars) "The repro is fixed. Now I should check if there are any other cases to consider.
The indices can be a single integer or ..."
[ 226.6s] 🔧 run_command (15 lines) python3 - <<'PY'
[ 227.1s] → Result: [
[ 268.7s] 💭 (2019 chars) "It seems PyArrow just uses the first few elements of `replacements` that match the number
of `True` values.
Wait, wait. ..."
[ 268.7s] 🔧 run_command grep -rn "test_scatter" tests/
[ 268.7s] → tests/series_only/scatter_test.py:9:def test_scatter(constructor_eager: ConstructorEager) -> None:
[ 271.4s] 💭 (43 chars) "Let's run these tests and see if they pass."
[ 271.4s] 🔧 run_command pytest tests/series_only/scatter_test.py -q --tb=short --no-header
[ 273.0s] → ..................... [100%]
[ 275.1s] 💭 (81 chars) "All passed.
Wait, let's check if there are tests for duplicate indices in there."
[ 275.1s] 📖 read_file (tests/series_only/scatter_test.py)
[ 275.1s] ✓ {'status': 'ok', 'filepath': 'tests/series_only/scatter_test.py', 'content': 'from __future__ import
annotations\n\nimpo…
[ 308.6s] 💭 (1345 chars) "No duplicate indices in the tests.
Let's check the return type.
`pc_replace_with_mask` returns a `ChunkedArray` or `Arr..."
[ 308.6s] 🔧 run_command (16 lines) python3 - <<'PY'
[ 309.0s] → Error: Replacements must be array or scalar, not ChunkedArray([
[ 365.9s] 💭 (3377 chars) "Aha! So `replacements` MUST be an `Array`, not a `ChunkedArray`.
In `narwhals/_arrow/series.py`:
```python
if i..."
[ 365.9s] 🔧 run_command git status --short && git diff
[ 365.9s] → M narwhals/_arrow/series.py
[ 428.3s] 💭 (18 chars) "The diff is clean."
[ 428.3s] 🤖 submit_patch
[ 428.4s] → submit_patch: {"status": "ok", "patch_size": 572, "files_changed": 1}
[ 437.4s] 💭 (39 chars) "OK. I've fixed the bug and verified it."
[ 437.4s] ✅ Agent finished: The `ArrowSeries.scatter` method in the `pyarrow` backend was incorrectly calling
`.take(indices_native)` on the replacement values, which led to `Index out of bounds` errors when the provided
indices...
Native result row
{
"agent_error": null,
"duration_seconds": 444.31,
"error": null,
"grade": {
"collected_tests": 25,
"competition_junit_ok": true,
"error": null,
"required_issues_count": 0,
"resolved": true,
"status_counts": {
"PASSED": 25
},
"strict_clean_patch": true,
"test_exit_code": 0
},
"instance_id": "narwhals-dev__narwhals-2864",
"pass_idx": 0,
"patch_chars": 572,
"phase1_seconds": 441.62,
"repo": "narwhals-dev/narwhals",
"request_log_path": "/kaggle-root/working/r31/rollouts_X/requests/narwhals-dev__narwhals-2864__p0__r3.jsonl",
"resolved": true,
"rollout_idx": 3,
"run_key": "narwhals-dev__narwhals-2864__p0__r3",
"strict_clean_patch": true,
"tool_calls": 16,
"total_llm_calls": 18,
"trace_path": "/kaggle-root/working/r31/rollouts_X/traces/trace_narwhals-dev__narwhals-2864__p0__r3.json"
}