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String literals are not interned if in a tuple #70336

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serhiy-storchaka opened this issue Jan 18, 2016 · 3 comments
Closed

String literals are not interned if in a tuple #70336

serhiy-storchaka opened this issue Jan 18, 2016 · 3 comments
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interpreter-core (Objects, Python, Grammar, and Parser dirs) performance Performance or resource usage

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@serhiy-storchaka
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BPO 26148
Nosy @brettcannon, @birkenfeld, @rhettinger, @ncoghlan, @vstinner, @benjaminp, @serhiy-storchaka, @1st1
Superseder
  • bpo-27942: Default value identity regression
    		•

    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 = None
closed_at = <Date 2016-09-25.10:44:49.457>
created_at = <Date 2016-01-18.20:09:48.624>
labels = ['interpreter-core', 'performance']
title = 'String literals are not interned if in a tuple'
updated_at = <Date 2016-09-25.10:44:49.456>
user = 'https://github.com/serhiy-storchaka'

    bugs.python.org fields:

    activity = <Date 2016-09-25.10:44:49.456>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2016-09-25.10:44:49.457>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2016-01-18.20:09:48.624>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 26148
keywords = []
message_count = 3.0
messages = ['258542', '258594', '277361']
nosy_count = 8.0
nosy_names = ['brett.cannon', 'georg.brandl', 'rhettinger', 'ncoghlan', 'vstinner', 'benjamin.peterson', 'serhiy.storchaka', 'yselivanov']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '27942'
type = 'performance'
url = 'https://bugs.python.org/issue26148'
versions = ['Python 3.6']
    @serhiy-storchaka
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    Usually string literals are interned. But not if they are a part of constant tuple.

    >>> def abc(): pass
... 
>>> x = 'abc'
>>> x is abc.__name__
True
>>> x = ('abc',)
>>> x[0] is abc.__name__
False

    This makes effect on namedtuples (bpo-25981). May make effect on __slots__ or other uses of constant tuples since searching a value in a tuple when values are not identical is a little slower that when they are identical.

    @serhiy-storchaka serhiy-storchaka added the interpreter-core (Objects, Python, Grammar, and Parser dirs) label Jan 18, 2016
    @vstinner vstinner added the performance Performance or resource usage label Jan 19, 2016
    @vstinner
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    FYI fatoptimizer has a more efficient algorithm to merge constants:
    http://fatoptimizer.readthedocs.org/en/latest/optimizations.html#comparison-with-the-peephole-optimizer

    It looks like it interns strings which are part of tuples. To be honest, I don't understand how it works, but it works :-)

    @serhiy-storchaka
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    The patch is provided in bpo-27942.

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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