ENH: Add columns parameter to from_dict #19802
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doc/source/whatsnew/v0.23.0.txt
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| @@ -589,6 +589,7 @@ Other API Changes | |||
| - :func:`Series.to_csv` now accepts a ``compression`` argument that works in the same way as the ``compression`` argument in :func:`DataFrame.to_csv` (:issue:`18958`) | |||
| - Set operations (union, difference...) on :class:`IntervalIndex` with incompatible index types will now raise a ``TypeError`` rather than a ``ValueError`` (:issue:`19329`) | |||
| - :class:`DateOffset` objects render more simply, e.g. ``<DateOffset: days=1>`` instead of ``<DateOffset: kwds={'days': 1}>`` (:issue:`19403`) | |||
| - :func:`DataFrame.from_dict` now accepts a ``columns`` argument that can be used to specify the column names when ``orient='index'`` is used (:issue:`18529`) | |||
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you can move it to the 'Other Enhancements' section
| elif orient == 'columns': | ||
| if columns is not None: | ||
| raise ValueError("cannot use columns parameter with " | ||
| "orient='columns'") |
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In principle, we could even allow it for orient='columns', as DataFrame(dict, columns=..) will just handle this fine.
But, not really sure of the value here.
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Could you expand on what you mean? If I pass a dict with columns to DataFrame() I get:
In [1]: pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]}, columns = ['one', 'two'])
Out[1]:
Empty DataFrame
Columns: [one, two]
Index: []
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Yes, that is exactly what I meant. The columns keyword does a 'reindexing' operation, and does not 'overwrite' if the data has keys as well. That's the current behaviour of DataFrame(..). So we could follow here the same pattern, but since this is sometimes also somewhat surprising behaviour, not sure if it is needed to have that here as well.
So therefore my doubt :-)
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Ah yes I understand now. It makes more sense to me to raise a ValueError in the case with from_dict(..., orient='columns', columns=[...]) but I can change it to not raise if we want to be consistent with DataFrame(dict, columns=[..])
reidy-p
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@@ Coverage Diff @@
## master #19802 +/- ##
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- Coverage 91.61% 91.59% -0.03%
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Files 150 150
Lines 48892 48895 +3
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- Hits 44792 44783 -9
- Misses 4100 4112 +12
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I believe we need to do a small doc change in dsintro.rst? (which motivated this). can you add on. lgtm. ping on green. |
I had that already in a branch, so will push that separately. |
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Thanks @reidy-p ! |
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See #19837 |
git diff upstream/master -u -- "*.py" | flake8 --diff@jorisvandenbossche it seems to have been quite straightforward to implement this but let me know if I missed anything.