STINNER Victor added the comment:
str.translate() currently allocates a buffer of UCS4 characters.
translate_writer.patch:
- modify _PyUnicode_TranslateCharmap() to use the _PyUnicodeWriter API
- drop optimizations for error handlers different than "ignore" because there
is no unit tests for them, and str.translate() uses "ignore". It's safer to
drop untested optimization.
- cleanup also the code: charmaptranslate_output() is now responsible to handle
charmaptranslate_lookup() result (to decrement the reference coutner)
str.translate() may be a little bit faster when translating ASCII to ASCII for
large string, but not so much.
bytes.translate() is much faster because it builds a C array of 256 items to
fast table lookup, whereas str.translate() requires a Python dict lookup for
each character, which is much slower.
codecs.charmap_build() (PyUnicode_BuildEncodingMap()) creates a C array ("a
three-level trie") for fast lookup. It is used with codecs.charmap_encode() for
8-bit encodings. We may reuse it for simple cases, like translating ASCII to
ASCII.
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keywords: +patch
Added file: http://bugs.python.org/file34691/translate_writer.patch
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