ENH: Add lazy copy to align #50432
ENH: Add lazy copy to align #50432
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Whatsnew entry? |
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We did not add entries for any of those, but can discuss this maybe in the next dev call and then add all at once? |
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Sounds good. IMO I think we should add an entry for these methods that get a CoW benefit |
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Sounds good to me, we should also add a whatsnew in 1.5.0 explaining how to try it out. I’ll make prs for this in the coming days after compiling the prs that were already merged |
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Thanks @phofl |
| left = self._reindex_indexer(join_index, lidx, copy) | ||
| elif lidx is None or join_index is None: | ||
| left = self.copy() if copy else self | ||
| left = self.copy(deep=copy) if copy or copy is None else self |
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Does this mean there are still cases where self is being returned? (if you manually specify copy=False)
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In [1]: s1 = pd.Series([1, 2, 3])
In [2]: s2 = pd.Series([4, 5, 6])
In [3]: s11, s22 = s1.align(s2, copy=False)
In [4]: s11 is s1
Out[4]: True
In [5]: s11.iloc[0] = 10
In [6]: s1
Out[6]:
0 10
1 2
2 3
dtype: int64
Of course, this is also because copy is already an existing keyword, so we don't just do self = self.copy(deep=None) under the hood as in other methods that in the past always returned a copy.
But for other methods that already have a copy keyword, I think for now we used copy=False to also mean shallow/lazy copy like copy=None with CoW enabled.
(it's also something we still need to discuss in general what to do with those copy keywords)
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But for other methods that already have a copy keyword, I think for now we used
copy=Falseto also mean shallow/lazy copy likecopy=Nonewith CoW enabled.
Actually, that's not fully correct. It seems this depends on case by case depending on how it is implemented, and we didn't consistently cover this case. Will open a dedicated issue for this topic: #50535
| return self.copy() | ||
| if copy or copy is None: | ||
| return self.copy(deep=copy) | ||
| return self |
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doc/source/whatsnew/vX.X.X.rstfile if fixing a bug or adding a new feature.