[mypyc] Add librt.strings.isalpha codepoint primitive#21521
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Wraps `Py_UNICODE_ISALPHA` for the codepoint fast path, mirroring the already-merged `librt.strings.isspace` (python#21462), `isdigit` (python#21504), and the in-flight `isalnum`. Microbenchmark, both paths mypyc-compiled, scanning 2.5M codepoints per call: `s[i].isalpha()` runs at ~17.8 ns/codepoint; the codepoint path `c: i32 = i32(ord(s[i])); isalpha(c)` at ~3.5 ns/codepoint, roughly 5x faster. (`str.isalpha()` walks the full Unicode category database per character; the codepoint path goes straight through the `Py_UNICODE_ISALPHA` macro with no `str` materialization.)
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
p-sawicki
approved these changes
May 20, 2026
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4th PR of #21418
This is 5x faster than
str.isalpha()for ASCII.