Eli Bendersky <[email protected]> added the comment:
I wonder if this is a fair comparison, Serhiy. Strings are unicode underneath,
so they have a large overhead per string (more data to copy around). Increasing
the length of the strings changes the game because due to PEP 393, the overhead
for ASCII-only Unicode strings is constant:
>>> import sys
>>> sys.getsizeof('a')
50
>>> sys.getsizeof(b'a')
34
>>> sys.getsizeof('a' * 1000)
1049
>>> sys.getsizeof(b'a' * 1000)
1033
>>>
When re-running your tests with larger chunks, the results are quite
interesting:
$ ./python -m timeit -s "import io; d=[b'a'*100,b'bb'*50,b'ccc'*50]*1000"
"b=io.BytesIO(); w=b.write" "for x in d: w(x)" "b.getvalue()"
1000 loops, best of 3: 509 usec per loop
$ ./python -m timeit -s "import io; d=['a'*100,'bb'*50,'ccc'*50]*1000"
"s=io.StringIO(); w=s.write" "for x in d: w(x)" "s.getvalue()"
1000 loops, best of 3: 282 usec per loop
So, it seems to me that BytesIO could use some optimization!
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