gh-144380: Fix incorrect type check in buffered_iternext()
#144381
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colesbury
added
needs backport to 3.13
The condition used Py_IS_TYPE(tp, ...) where tp is already a `type`, this made the fast path unreachable. Avoid unnecessary method resolution checks in the iteration hot path, resulting in ~49% faster line iteration for `io.BufferedReader`.
ruiyangke
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Thanks, new entry added |
cmaloney
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Feb 2, 2026
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Fix incorrect type check in
buffered_iternext()that prevented the fast path from ever being taken, slowing down iteration over buffered binary files.Since
tpis already a type object,Py_IS_TYPE(tp, X)expands toPy_TYPE(tp) == X, which compares thetypeitself againstBufferedReader. This is always false, so the fast path was never taken.pyperf benchmark:
Closes: #144380
buffered_iternextis never taken due to incorrect type check #144380