[Broyojo]

collections.UserString.replace() called its third parameter maxsplit, so UserString('aa').replace('a', 'b', count=1) raised TypeError even though str.replace() has accepted count as a keyword since 3.13. This renames it to count to match str.replace().

The existing test_count_keyword in Lib/test/string_tests.py called replace on str literals, so it never ran against UserString (or bytes/bytearray). It now goes through checkequal, which exercises every type that shares these tests.

Compatibility: a caller passing maxsplit= by keyword now gets TypeError. That name was never documented and str.replace() never accepted it, and I found no callers in the stdlib.

• Issue: collections.UserString.replace() rejects the count keyword #161970

[chatgpt-codex-connector]

Codex Review Summary: ✅ Completed

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-14T00:28:09.854564Z	9d45abf	PR opened

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