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DEPR: deprecate pd.lreshape#64731

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jbrockmendel wants to merge 5 commits intopandas-dev:mainfrom
jbrockmendel:depr-34313-34314
Draft

DEPR: deprecate pd.lreshape#64731
jbrockmendel wants to merge 5 commits intopandas-dev:mainfrom
jbrockmendel:depr-34313-34314

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Summary

  • Deprecate pd.lreshape with Pandas4Warning, directing users to pd.melt instead
  • GitHub code search shows virtually no real-world usage (~3-5 genuine callers outside pandas)

closes #34313

Test plan

  • Existing TestLreshape tests updated to assert the deprecation warning
  • Pre-commit hooks pass

🤖 Generated with Claude Code

jbrockmendel and others added 4 commits March 11, 2026 17:03
…ions

Replace kh_get + kh_put patterns with kh_put alone (checking ret for
new-vs-existing), removing a redundant hash computation and probe
per element in value_count, _unique, duplicated(keep=False), and
get_labels_groupby.

Also clean up the vendored khash.h:
- Remove dead deletion-tracking code from kh_put/kh_get (deletions
  are disabled via __ac_isdel=0, but site variable and branches remained)
- Fix kh_clear to use 0xff (all-empty) instead of 0xaa, which was a
  leftover from the original 2-bit-per-slot flag scheme
- Remove unreachable shrink path from kh_put resize trigger
- Fix value_count object pre-sizing from n//10 to n

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Deprecate pd.lreshape in favor of pd.melt. lreshape has virtually no
real-world usage outside of pandas.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jbrockmendel jbrockmendel added the Deprecate Functionality to remove in pandas label Mar 19, 2026
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jbrockmendel jbrockmendel marked this pull request as draft March 20, 2026 00:11
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DEPR: pd.lreshape

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