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PERF: avoid unneeded recoding of categoricals and reuse CategoricalDtypes for greater slicing speed #21659

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Jun 29, 2018
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PERF: avoid unneeded recoding of categoricals and reuse CategoricalDtypes for greater slicing speed #21659

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ed1928f
avoid unneeded recoding af categoricals
Jun 27, 2018
ff2de3f
adjusted for comments
Jun 28, 2018
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tp committed Jun 28, 2018
commit ff2de3facbece7f04d7f865f68835744f079f238
3 changes: 3 additions & 0 deletions doc/source/whatsnew/v0.24.0.txt
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Expand Up @@ -134,6 +134,9 @@ Removal of prior version deprecations/changes
Performance Improvements
~~~~~~~~~~~~~~~~~~~~~~~~

- Very large improvement in performance of slicing when the index is a :class:`CategoricalIndex`,
both when indexing by label (using .loc) and position(.iloc).
Likewise, slicing a ``CategoricalIndex`` itself (i.e. ``ci[100:200]``) shows similar speed improvements (:issue:`21659`)
- Improved performance of :func:`Series.describe` in case of numeric dtpyes (:issue:`21274`)
- Improved performance of :func:`pandas.core.groupby.GroupBy.rank` when dealing with tied rankings (:issue:`21237`)
- Improved performance of :func:`DataFrame.set_index` with columns consisting of :class:`Period` objects (:issue:`21582`,:issue:`21606`)
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5 changes: 2 additions & 3 deletions pandas/core/dtypes/dtypes.py
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Expand Up @@ -195,10 +195,9 @@ def __eq__(self, other):
"""
if isinstance(other, compat.string_types):
return other == self.name

if other is self:
elif other is self:
return True
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prob doesn't make any difference, but this could be elif (existing if)

if not (hasattr(other, 'ordered') and hasattr(other, 'categories')):
elif not (hasattr(other, 'ordered') and hasattr(other, 'categories')):
return False
elif self.categories is None or other.categories is None:
# We're forced into a suboptimal corner thanks to math and
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