fix: fix pyarrow len aggregation behaviour for depth-1 exprs
#1589
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AlessandroMiola
commented
Dec 14, 2024
Comment on lines
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| @pytest.mark.parametrize( | ||
| ("expr", "expected"), | ||
| [ | ||
| (nw.col("b").sum(), {"a": [1, 2], "b": [3, 3]}), | ||
| (nw.col("b").mean(), {"a": [1, 2], "b": [1.5, 3]}), | ||
| (nw.col("b").max(), {"a": [1, 2], "b": [2, 3]}), | ||
| (nw.col("b").min(), {"a": [1, 2], "b": [1, 3]}), | ||
| (nw.col("b").std(), {"a": [1, 2], "b": [0.707107, None]}), | ||
| (nw.col("b").len(), {"a": [1, 2], "b": [3, 1]}), | ||
| (nw.col("b").n_unique(), {"a": [1, 2], "b": [3, 1]}), | ||
| (nw.col("b").count(), {"a": [1, 2], "b": [2, 1]}), | ||
| ], | ||
| ) | ||
| def test_group_by_depth_1_agg( | ||
| constructor: Constructor, | ||
| expr: nw.Expr, | ||
| expected: dict[str, list[int | float]], | ||
| ) -> None: | ||
| data = {"a": [1, 1, 1, 2], "b": [1, None, 2, 3]} | ||
| result = nw.from_native(constructor(data)).group_by("a").agg(expr).sort("a") |
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Also median is failing here for pyarrow 🤔, reason why I've left it out and maintained the original test for it. Somehow, though, we're pointing it out in docs that median's results might slightly differ across backends due to differences in the underlying algorithms...
narwhals/_arrow/group_by.py
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| function_name = POLARS_TO_ARROW_AGGREGATIONS.get(function_name, function_name) | ||
|
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| option = get_function_name_option(function_name) | ||
| if expr._function_name != "col->len": | ||
| option = get_function_name_option(function_name) | ||
| else: | ||
| option = pc.CountOptions(mode="all") |
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would it be cleaner to have
function_name, option = POLARS_TO_ARROW_AGGREGATIONS[function_name]
, and map to all the options in POLARS_TO_ARROW_AGGREGATIONS?
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Adds a specific condition for dealing with pyarrow depth-1
lenexpressions in group-by contexts.