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GeezerVison is showing github.com — [mypyc] Add primitives for str.islower, isupper and istitle by Jahongir-Qurbonov · Pull Request #22405 · python/mypy

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Jahongir-Qurbonov commented Nov 9, 2026

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Add primitives for str.islower(), str.isupper() and str.istitle().

The implementations mirror CPython's and have a fast path for ASCII strings (which have no titlecase characters). str.islower() and str.isupper() share a helper.

Tests compare the results against CPython for every code point (alone and combined with cased ASCII characters), and for a set of multi-character strings including titlecase characters such as ǅ.

The annotate test that used str.islower() as an example of a non-native method call now uses str.expandtabs() instead.

Micro-benchmark (2M iterations over 11 short strings, compiled code, generic method call through Any vs the new primitive, Python 3.13):

Method	Before	After
`islower`	0.362s	0.129s
`isupper`	0.337s	0.104s
`istitle`	0.375s	0.159s

Part of mypyc/mypyc#644.

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          [mypyc] Add primitives for str.islower, isupper and istitle

5e10ced

The implementations mirror CPython and use a fast path for ASCII strings.
str.islower() and str.isupper() share a helper.

The annotate test that used str.islower() as an example of a non-native method
call now uses str.expandtabs() instead.

Part of mypyc/mypyc#644.

Jahongir-Qurbonov mentioned this pull request

Nov 10, 2026

More primitives mypyc/mypyc#644

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JukkaL commented Nov 12, 2026

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This now has a merge conflict, can you rebase?

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Jahongir-Qurbonov added 2 commits

November 12, 2026 16:49


          Merge remote-tracking branch 'upstream/master' into mypyc-str-is-cased

04858ba

# Conflicts:
#	mypyc/doc/str_operations.rst
#	mypyc/lib-rt/CPy.h
#	mypyc/lib-rt/str_ops.c
#	mypyc/primitives/str_ops.py
#	mypyc/test-data/fixtures/ir.py
#	mypyc/test-data/irbuild-str.test
#	mypyc/test-data/run-strings.test


          Only check a sample of non-BMP code points in tests

03b6d1d

Jahongir-Qurbonov mentioned this pull request

Nov 12, 2026

[mypyc] Only check a sample of non-BMP code points in str tests #22448

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