From 257b34558b91ef4a11a0d5caccc79c7d56d67f07 Mon Sep 17 00:00:00 2001 From: Ruiyang Ke Date: Sun, 1 Feb 2026 03:42:33 -0800 Subject: [PATCH] gh-144380: Fix incorrect type check in buffered_iternext() 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`. --- .../Library/2026-02-01-15-25-00.gh-issue-144380.U7py_s.rst | 1 + Modules/_io/bufferedio.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2026-02-01-15-25-00.gh-issue-144380.U7py_s.rst diff --git a/Misc/NEWS.d/next/Library/2026-02-01-15-25-00.gh-issue-144380.U7py_s.rst b/Misc/NEWS.d/next/Library/2026-02-01-15-25-00.gh-issue-144380.U7py_s.rst new file mode 100644 index 00000000000000..4b5b1b3776d735 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-02-01-15-25-00.gh-issue-144380.U7py_s.rst @@ -0,0 +1 @@ +Improve performance of :class:`io.BufferedReader` line iteration by ~49%. diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c index 6d779abd89ca84..0fdae7b2d21004 100644 --- a/Modules/_io/bufferedio.c +++ b/Modules/_io/bufferedio.c @@ -1505,8 +1505,8 @@ buffered_iternext(PyObject *op) _PyIO_State *state = find_io_state_by_def(Py_TYPE(self)); tp = Py_TYPE(self); - if (Py_IS_TYPE(tp, state->PyBufferedReader_Type) || - Py_IS_TYPE(tp, state->PyBufferedRandom_Type)) + if (tp == state->PyBufferedReader_Type || + tp == state->PyBufferedRandom_Type) { /* Skip method call overhead for speed */ line = _buffered_readline(self, -1);