Update groupby().first() documentation to clarify behavior with missing data (#27578) #61345
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ericcht
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ericcht
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rhshadrach
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Apr 24, 2025
| @@ -3232,9 +3232,12 @@ def first( | |||
| self, numeric_only: bool = False, min_count: int = -1, skipna: bool = True | |||
| ) -> NDFrameT: | |||
| """ | |||
| Compute the first entry of each column within each group. | |||
| Compute the first non-null entry of each column within each group. | |||
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pandas documentation is quite consistent with using NA instead of null. Can you use NA throughout.
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In addition, this line is incorrect as you can pass skipna=False.
| core.groupby.DataFrameGroupBy.nth : Take the nth row from each group. | ||
| DataFrame.groupby : Group DataFrame using a mapper or by a Series of columns. | ||
| Series.groupby : Group Series using a mapper or by a Series of values. | ||
| GroupBy.nth : Take the nth row from each group. |
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GroupBy is not public. Can you use DataFrameGroupBy instead.
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| >>> df.groupby("A").nth(0) | ||
| B C D | ||
| A | ||
| 1 NaN 1 2000-03-11 | ||
| 3 6.0 3 2000-03-13 |
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I think this page should only include documentation on first. Can you remove the use of other methods.
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This PR enhances the docstring for
GroupBy.first()to clarify:.nth(0)and.head(1)in how it treats missing valuesFixes part of issue #27578
Ready for review.