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Avoid nonneeded use of PyUnicode_FromObject() #70245
Description
| BPO | 26057 |
|---|---|
| Nosy | @ncoghlan, @vstinner, @vadmium, @serhiy-storchaka |
| Files |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2016-04-13.12:45:58.826>
created_at = <Date 2016-01-09.08:41:41.041>
labels = ['interpreter-core', 'type-feature']
title = 'Avoid nonneeded use of PyUnicode_FromObject()'
updated_at = <Date 2016-04-14.09:31:23.514>
user = 'https://github.com/serhiy-storchaka'bugs.python.org fields:
activity = <Date 2016-04-14.09:31:23.514>
actor = 'python-dev'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2016-04-13.12:45:58.826>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2016-01-09.08:41:41.041>
creator = 'serhiy.storchaka'
dependencies = []
files = ['41541', '42421']
hgrepos = []
issue_num = 26057
keywords = ['patch']
message_count = 8.0
messages = ['257806', '257807', '263125', '263128', '263326', '263332', '263333', '263392']
nosy_count = 5.0
nosy_names = ['ncoghlan', 'vstinner', 'python-dev', 'martin.panter', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue26057'
versions = ['Python 3.6']
Activity
serhiy-storchaka commentedon Jan 9, 2016
In Python 2 PyUnicode_FromObject() was used for coercing 8-bit strings to unicode by decoding them with the default encoding. But in Python 3 there is no such coercing. The effect of PyUnicode_FromObject() in Python 3 is ensuring that the argument is a string and convert an instance of str subtype to exact str. The latter often is just a waste of memory and time, since resulted string is used only for retrieving UTF-8 representation or raw data.
Proposed patch makes following things:
Example of performance gain:
Unpatched:
$ ./python -m timeit -s "a = 'a'*100; b = 'b'*1000" -- "a in b"
1000000 loops, best of 3: 0.404 usec per loop
$ ./python -m timeit -s "class S(str): pass" -s "a = S('a'*100); b = S('b'*1000)" -- "a in b"
1000000 loops, best of 3: 0.723 usec per loop
Patched:
$ ./python -m timeit -s "a = 'a'*100; b = 'b'*1000" -- "a in b"
1000000 loops, best of 3: 0.383 usec per loop
$ ./python -m timeit -s "class S(str): pass" -s "a = S('a'*100); b = S('b'*1000)" -- "a in b"
1000000 loops, best of 3: 0.387 usec per loop
serhiy-storchaka commentedon Jan 9, 2016
See also bpo-15984 about correcting the documentation of PyUnicode_FromObject().
vadmium commentedon Apr 10, 2016
Left some comments
serhiy-storchaka commentedon Apr 10, 2016
Updated patch addresses Martin's comments.
vadmium commentedon Apr 13, 2016
Apart from one redundancy (see review), this looks good to me.
python-dev commentedon Apr 13, 2016
New changeset 3f3b3d4881f6 by Serhiy Storchaka in branch 'default':
Issue bpo-26057: Got rid of nonneeded use of PyUnicode_FromObject().
https://hg.python.org/cpython/rev/3f3b3d4881f6
serhiy-storchaka commentedon Apr 13, 2016
Thank you for your review Martin.
python-dev commentedon Apr 14, 2016
New changeset 19dec08e54a8 by Serhiy Storchaka in branch 'default':
Issues bpo-26716, bpo-26057: Regenerate Argument Clinic code.
https://hg.python.org/cpython/rev/19dec08e54a8