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DOC: whatsnew for the improvement to warning messages #44419

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Nov 13, 2021
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DOC: whatsnew for the improvement to warning messages #44419

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DOC: whatsnew for the improvement to warning messages
rhshadrach Nov 12, 2021
7436312
fixup
rhshadrach Nov 12, 2021
365d15b
fixup
rhshadrach Nov 12, 2021
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25 changes: 25 additions & 0 deletions doc/source/whatsnew/v1.4.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,31 @@ including other versions of pandas.
Enhancements
~~~~~~~~~~~~

.. _whatsnew_140.enhancements.warning_lineno:

Improved warning messages
^^^^^^^^^^^^^^^^^^^^^^^^^

Previously, warning messages may have pointed to lines within the pandas library. Running the script ``setting_with_copy_warning.py``

.. code-block:: python

import pandas as pd

df = pd.DataFrame({'a': [1, 2, 3]})
df[:2].loc[:, 'a'] = 5

with pandas 1.3 resulted in::

.../site-packages/pandas/core/indexing.py:1951: SettingWithCopyWarning:
A value is trying to be set on a copy of a slice from a DataFrame.

This made it difficult to determine where the warning was being generated from. Now pandas will inspect the call stack, reporting the first line outside of the pandas library that gave rise to the warning. The output of the above script is now::

setting_with_copy_warning.py:4: SettingWithCopyWarning:
A value is trying to be set on a copy of a slice from a DataFrame.


.. _whatsnew_140.enhancements.numeric_index:

More flexible numeric dtypes for indexes
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