feat(typing): Add IntoDType alias
#2654
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dangotbanned
added
enhancement
|
@MarcoGorelli sorry I butchered a rebase 😭 |
dangotbanned
commented
Jun 7, 2025
Comment on lines
+365
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+391
| IntoDType: TypeAlias = "dtypes.DType | type[NonNestedDType]" | ||
| """Anything that can be converted into a Narwhals DType. | ||
|
|
||
| Examples: | ||
| >>> import polars as pl | ||
| >>> import narwhals as nw | ||
| >>> df_native = pl.DataFrame({"a": [1, 2, 3], "b": [4.0, 5.0, 6.0]}) | ||
| >>> df = nw.from_native(df_native) | ||
| >>> df.select( | ||
| ... nw.col("a").cast(nw.Int32), | ||
| ... nw.col("b").cast(nw.String()).str.split(".").cast(nw.List(nw.Int8)), | ||
| ... ) | ||
| ┌──────────────────┐ | ||
| |Narwhals DataFrame| | ||
| |------------------| | ||
| |shape: (3, 2) | | ||
| |┌─────┬──────────┐| | ||
| |│ a ┆ b │| | ||
| |│ --- ┆ --- │| | ||
| |│ i32 ┆ list[i8] │| | ||
| |╞═════╪══════════╡| | ||
| |│ 1 ┆ [4, 0] │| | ||
| |│ 2 ┆ [5, 0] │| | ||
| |│ 3 ┆ [6, 0] │| | ||
| |└─────┴──────────┘| | ||
| └──────────────────┘ | ||
| """ |
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The logic I'm following for this is that we use IntoDType for anything that can trigger a cast.
Or another way to look at it is if the call reaches into _<backend>.utils.<thing>_to_<other>_dtype then this should warn when you're likely to raise
dangotbanned
commented
Jun 11, 2025
| @@ -125,7 +125,7 @@ def test_cast_to_enum_vmain( | |||
| with pytest.raises( | |||
| ValueError, match="Can not cast / initialize Enum without categories present" | |||
| ): | |||
| df_nw.select(col_a.cast(nw.Enum)) | |||
| df_nw.select(col_a.cast(nw.Enum)) # type: ignore[arg-type] | |||
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Not sure if this got lost, but needing these ignores is a positive outcome 🙂
FBruzzesi
reviewed
Jun 12, 2025
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Thanks @dangotbanned - it's look pretty straightforward and definitly a nice improvement to be able to differentiate nested vs non-nested dtypes.
I only have a tiny question
| @@ -125,7 +125,7 @@ def test_cast_to_enum_vmain( | |||
| with pytest.raises( | |||
| ValueError, match="Can not cast / initialize Enum without categories present" | |||
| ): | |||
| df_nw.select(col_a.cast(nw.Enum)) | |||
| df_nw.select(col_a.cast(nw.Enum)) # type: ignore[arg-type] | |||
|
nice one, thanks both! |
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Closes #2626
What type of PR is this? (check all applicable)
Related issues
IntoDTypealias, replaceDType | type[DType]#2626Checklist
If you have comments or can explain your changes, please do so below
I think
selectorsare safe as-is, but will follow that up separately if needed