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In the re's token example OP and SKIP regexes can be improved #66176

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py-user mannequin opened this issue Jul 14, 2014 · 3 comments
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In the re's token example OP and SKIP regexes can be improved #66176

py-user mannequin opened this issue Jul 14, 2014 · 3 comments
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@rhettinger
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docs Documentation in the Doc dir performance Performance or resource usage topic-regex

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py-user mannequin commented Jul 14, 2014

BPO 21977
Nosy @rhettinger, @ezio-melotti, @py-user
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  • re_ex_tok.diff: clear OP and fast SKIP
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    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/rhettinger'
closed_at = <Date 2014-07-14.08:53:36.476>
created_at = <Date 2014-07-14.07:23:21.527>
labels = ['expert-regex', 'docs', 'performance']
title = "In the re's token example OP and SKIP regexes can be improved"
updated_at = <Date 2014-07-14.15:23:42.385>
user = 'https://github.com/py-user'

    bugs.python.org fields:

    activity = <Date 2014-07-14.15:23:42.385>
actor = 'berker.peksag'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2014-07-14.08:53:36.476>
closer = 'rhettinger'
components = ['Documentation', 'Regular Expressions']
creation = <Date 2014-07-14.07:23:21.527>
creator = 'py.user'
dependencies = []
files = ['35951']
hgrepos = []
issue_num = 21977
keywords = ['patch']
message_count = 3.0
messages = ['223000', '223003', '223004']
nosy_count = 6.0
nosy_names = ['rhettinger', 'ezio.melotti', 'mrabarnett', 'docs@python', 'py.user', 'python-dev']
pr_nums = []
priority = 'low'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue21977'
versions = ['Python 3.4', 'Python 3.5']
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    py-user mannequin commented Jul 14, 2014

    https://docs.python.org/3/library/re.html#writing-a-tokenizer

    There are redundant escapes in the regex:

    ('OP', r'[+*\/\-]'), # Arithmetic operators

    Sequence -+*/ is sufficient.

    It makes the loop to do all steps on every 4 spaces:

    ('SKIP', r'[ \t]'), # Skip over spaces and tabs

    Sequence [ \t]+ is faster.

    Applied patch.

    @py-user py-user mannequin assigned docspython Jul 14, 2014
    @py-user py-user mannequin added type-feature A feature request or enhancement docs Documentation in the Doc dir topic-regex labels Jul 14, 2014
    @rhettinger rhettinger assigned rhettinger and unassigned docspython Jul 14, 2014
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    I will keep the \- because the - at the front of the character range is a non-obvious special case. The other changes look reasonable.

    @rhettinger rhettinger added performance Performance or resource usage and removed type-feature A feature request or enhancement labels Jul 14, 2014
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    python-dev mannequin commented Jul 14, 2014

    New changeset bb28542af060 by Raymond Hettinger in branch '3.4':
    bpo-21977: Minor improvements to the regexes in the tokenizer example.
    http://hg.python.org/cpython/rev/bb28542af060

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