Skip to content

gh-144157: Optimize bytes.translate() by deferring change detection #144158

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
gpshead merged 2 commits into from
Jan 22, 2026
Merged

gh-144157: Optimize bytes.translate() by deferring change detection #144158

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
3bf238d
Optimize bytes.translate() by deferring change detection
gpshead Jan 22, 2026
46c1623
NEWS entry
gpshead Jan 22, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-01-22-16-20-16.gh-issue-144157.dxyp7k.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
:meth:`bytes.translate` now allows the compiler to unroll its loop more
usefully for a 2x speedup in the common no-deletions specified case.
14 changes: 9 additions & 5 deletions Objects/bytesobject.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2237,11 +2237,15 @@ bytes_translate_impl(PyBytesObject *self, PyObject *table,
/* If no deletions are required, use faster code */
for (i = inlen; --i >= 0; ) {
c = Py_CHARMASK(*input++);
if (Py_CHARMASK((*output++ = table_chars[c])) != c)
changed = 1;
}
if (!changed && PyBytes_CheckExact(input_obj)) {
Py_SETREF(result, Py_NewRef(input_obj));
*output++ = table_chars[c];
}
/* Check if anything changed (for returning original object) */
/* We save this check until the end so that the compiler will */
/* unroll the loop above leading to MUCH faster code. */
if (PyBytes_CheckExact(input_obj)) {
if (memcmp(PyBytes_AS_STRING(input_obj), output_start, inlen) == 0) {
Py_SETREF(result, Py_NewRef(input_obj));
}
}
PyBuffer_Release(&del_table_view);
PyBuffer_Release(&table_view);
Expand Down
Loading