22.03.19 09:45, Victor Stinner пише:
Internally, CPython has a _PyUnicodeWriter which is an efficient way
to create a string but appending substrings or characters.
_PyUnicodeWriter changes the internal storage format depending on
characters code points (ascii or latin1: 1 byte/character, BMP: 2 b/c,
full UCS: 4 b/c). I tried once to expose it in Python, but I wasn't
convinced by performances. The overhead of method calls was quite
significant, and I wasn't convinced by "writer += str" performance
neither. Maybe I should try again. PyPy also has such object. It
avoids the "str += str" hack in ceval.c to avoid very poor performance
(_PyUnicodeWriter also uses overallocation which can be controlled
with multiple parameters to reduce the number of realloc).
Another alternative would be have to add a "strarray" type similar to
bytes/bytearray couple.
Another alternative of mutable string buffer and string builder is
io.StringIO.
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