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[Python-Dev] cpython: Issue #22003: When initialized from a bytes object, io.BytesIO() now

Serhiy Storchaka storchaka at gmail.com
Wed Jul 30 08:11:24 CEST 2014 
30.07.14 06:59, Serhiy Storchaka написав(ла):
> 30.07.14 02:45, antoine.pitrou написав(ла):
>> http://hg.python.org/cpython/rev/79a5fbe2c78f
>> changeset:   91935:79a5fbe2c78f
>> parent:      91933:fbd104359ef8
>> user:        Antoine Pitrou <solipsis at pitrou.net>
>> date:        Tue Jul 29 19:41:11 2014 -0400
>> summary:
>>    Issue #22003: When initialized from a bytes object, io.BytesIO() now
>> defers making a copy until it is mutated, improving performance and
>> memory use on some use cases.
>>
>> Patch by David Wilson.
>
> Did you compare this with issue #15381 [1]?
>
> [1] http://bugs.python.org/issue15381

Using microbenchmark from issue22003:

$ cat i.py
import io
word = b'word'
line = (word * int(79/len(word))) + b'\n'
ar = line * int((4 * 1048576) / len(line))
def readlines():
     return len(list(io.BytesIO(ar)))
print('lines: %s' % (readlines(),))
$ ./python -m timeit -s 'import i' 'i.readlines()'

Before patch: 10 loops, best of 3: 46.9 msec per loop
After issue22003 patch: 10 loops, best of 3: 36.4 msec per loop
After issue15381 patch: 10 loops, best of 3: 27.6 msec per loop
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