feat: support __getitem__ with slices for columns
#839
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FBruzzesi
reviewed
Aug 22, 2024
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I left a tiny comment on a typo.
I wonder if it could be worth to:
- Add an example in the docstring of the method
- Add a note for the behavior since slicing here is
- If string: both start and stop are included
- If int: typical python behavior, start included and stop excluded
FBruzzesi
reviewed
Aug 22, 2024
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| - `df['a']` extracts column `'a'` and returns a `Series`. | ||
| - `df[0:2]` extracts the first two rows and returns a `DataFrame`. | ||
| - `df[0:2, 'a']` extracts the first two rows from column `'a'` and returns | ||
| a `Series`. | ||
| - `df[0:2, 0]` extracts the first two rows from the first column and returns | ||
| a `Series`. | ||
| - `df[[0, 1], [0, 1, 2]]` extracts the first two rows and the first three columns | ||
| and returns a `DataFrame` | ||
| - `df[0: 2, ['a', 'c']]` extracts the first two rows and columns `'a'` and `'c'` and | ||
| returns a `DataFrame` | ||
| - `df[:, 0: 2]` extracts all rows from the first two columns and returns a `DataFrame` | ||
| - `df[:, 'a': 'c']` extracts all rows and all columns positioned between `'a'` and `'c'` | ||
| _inclusive_ and returns a `DataFrame`. For example, if the columns are | ||
| `'a', 'b', 'c', 'd'`, then that would extract columns `'a'`, `'b'`, and `'c'`. |
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😄 thanks, maybe we should upstream this to Polars itself, there's zero docs on getitem there
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That's a good idea, I had never seen df[:, "a":"c"] in polars code and I was not aware that's even possible 😂
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Rendering may need one less indentation level:
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good points, thanks! I think this is easier to explain with examples |
This was referenced Aug 22, 2024
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I kinda wish we didn't have to go overboard with
__getitem__overloads, but scikit-learn are using this, so I think we shouldMy general thinking on this is: make sure that Narwhals is easily usable by scikit-learn. Then, it's their decision whether or not they adopt - but we should at least be ready
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