API / CoW: constructing Series from Series creates lazy copy (with default copy=False) #49524
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…fault copy=False)
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phofl
reviewed
Nov 5, 2022
mroeschke
reviewed
Nov 16, 2022
doc/source/whatsnew/v2.0.0.rst
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| @@ -77,6 +77,13 @@ be set to ``"pyarrow"`` to return pyarrow-backed, nullable :class:`ArrowDtype` ( | |||
| df_pyarrow = pd.read_csv(data, use_nullable_dtypes=True, engine="pyarrow") | |||
| df_pyarrow.dtypes | |||
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| Copy on write improvements | |||
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ | |||
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Added a new section like is being added in #50471. We can consolidate those different blurbs later on in a coherent whatsnew.
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I updated this to put the actual code change behind a "if CoW" check (so this PR only changes something for the case of CoW enabled), and will do a separate PR to address #49523 (and for both Series and DataFrame). |
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xref #48998 (bullet point about constructors)
In the CoW proposal, the idea for constructors would be that those follow the lazy copy with CoW approach as well, just like other methods and indexing operations that create a new Series/DataFrame from another Series/DataFrame.
That was not yet implemented in the initial implementation, and this PR is adding it for the
Series(series)case.Currently, the way I implemented this is by making a shallow copy of the manager. This however also affects the default (non-CoW) behaviour -> see #49523.
Depending on whether we are OK with changing ("fixing"?) that behaviour in 2.0 or not, I can leave this as is, or otherwise put the copy behind a
if get_cnofig("mode.copy_on_write")check.doc/source/whatsnew/vX.X.X.rstfile if fixing a bug or adding a new feature.