Return an object itself for some types in _PyCode_ConstantKey()

[serhiy-storchaka]

BPO	33299
Nosy	@vstinner, @serhiy-storchaka
PRs	bpo-33299: Return an object itself for some types in _PyCode_ConstantKey(). #6513

^{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 2018-04-19.05:28:42.537>
created_at = <Date 2018-04-17.16:54:12.351>
labels = ['interpreter-core', '3.8', 'performance']
title = 'Return an object itself for some types in _PyCode_ConstantKey()'
updated_at = <Date 2018-04-19.05:28:42.536>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2018-04-19.05:28:42.536>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2018-04-19.05:28:42.537>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2018-04-17.16:54:12.351>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 33299
keywords = ['patch']
message_count = 2.0
messages = ['315407', '315477']
nosy_count = 2.0
nosy_names = ['vstinner', 'serhiy.storchaka']
pr_nums = ['6513']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue33299'
versions = ['Python 3.8']

[serhiy-storchaka]

_PyCode_ConstantKey() wraps a constant into a tuple that contains other items besides the wrapped object. This makes booleans different from 0 and 1, makes numbers of different type different (1, 1.0 and 1.0+0j), makes floating point zeros with different signs different (0.0 and -0.0), and avoids a ByteWarning from comparing strings and bytes.

But for some types objects are always different from objects of other types and from tuples. _PyCode_ConstantKey() can be made faster and using less memory if return the object of these types unwrapped.

[serhiy-storchaka]

New changeset b7e1eff by Serhiy Storchaka in branch 'master':
bpo-33299: Return an object itself for some types in _PyCode_ConstantKey(). (GH-6513)
b7e1eff