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DOC: update copy keyword explanation in astype docstring #63274

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DOC: update copy keyword explanation in astype docstring #63274

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20 changes: 6 additions & 14 deletions pandas/core/generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6354,23 +6354,15 @@ def astype(
a numpy.dtype or Python type to cast one or more of the DataFrame's
columns to column-specific types.
copy : bool, default False
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@jorisvandenbossche jorisvandenbossche Dec 5, 2025

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Since no one should specify this keyword, we could also just leave out the type part entirely?

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copy : bool, default False
copy

(probably would need to suppress some numpydoc linting rule for this method, though)

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@rhshadrach rhshadrach Dec 5, 2025

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In general for a deprecated parameter, I think we should still keep the type/default/description even if we don't want users to use it. In this case I would update the description to something like

This keyword is now ignored; changing its value will have no impact on the method.

Return a copy when ``copy=True`` (be very careful setting
``copy=False`` as changes to values then may propagate to other
pandas objects).
.. deprecated:: 3.0.0

.. note::
The `copy` keyword will change behavior in pandas 3.0.
`Copy-on-Write
This keyword is ignored and will be removed in pandas 4.0. Since
pandas 3.0, this method always returns a new object using a lazy
copy mechanism that defers copies until necessary
(Copy-on-Write). See the `user guide on Copy-on-Write
<https://pandas.pydata.org/docs/dev/user_guide/copy_on_write.html>`__
will be enabled by default, which means that all methods with a
`copy` keyword will use a lazy copy mechanism to defer the copy and
ignore the `copy` keyword. The `copy` keyword will be removed in a
future version of pandas.

You can already get the future behavior and improvements through
enabling copy on write ``pd.options.mode.copy_on_write = True``
for more details.

.. deprecated:: 3.0.0
errors : {'raise', 'ignore'}, default 'raise'
Control raising of exceptions on invalid data for provided dtype.

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