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re.sub ignores flag re.M #86639

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re.sub ignores flag re.M#86639
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3.8 (EOL)end of lifetopic-IOtype-bugAn unexpected behavior, bug, or error

Description

@jlaurens
jlaurens
mannequin
opened on Nov 26, 2020
BPO 42473

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 2020-11-26.16:01:39.446>
created_at = <Date 2020-11-26.13:47:10.045>
labels = ['invalid', 'type-bug', '3.8', 'expert-IO']
title = 're.sub ignores flag re.M'
updated_at = <Date 2020-11-26.16:01:39.442>
user = 'https://bugs.python.org/jlaurens'

bugs.python.org fields:

activity = <Date 2020-11-26.16:01:39.442>
actor = 'mrabarnett'
assignee = 'none'
closed = True
closed_date = <Date 2020-11-26.16:01:39.446>
closer = 'mrabarnett'
components = ['IO']
creation = <Date 2020-11-26.13:47:10.045>
creator = 'jlaurens'
dependencies = []
files = []
hgrepos = []
issue_num = 42473
keywords = []
message_count = 2.0
messages = ['381901', '381905']
nosy_count = 2.0
nosy_names = ['mrabarnett', 'jlaurens']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42473'
versions = ['Python 3.8']

Activity

  1. jlaurens commented on Nov 26, 2020

    @jlaurens
    jlaurensmannequin
    on Nov 26, 2020
    MannequinAuthor

    Test code:

    import re
test='''012345678
         
012345678
'''
pattern = r'^\s+?$'
m = re.search(pattern, test, re.M)
if m:
    print(f'TEST FOUND "{m.span()}"')

    def replace(m):
        print(f'TEST REMOVE {m.span()}')
        return ''

    test = re.sub(pattern, replace, test, re.M)
    m = re.search(pattern, test, re.M)
    if m:
        print(f'TEST STILL THERE "{m.span()}"')

print('COMPILE PATTERN FIRST')
pattern_re = re.compile(pattern, re.M)
m = re.search(pattern_re, test)
if m:
    print(f'TEST FOUND "{m.span()}"')

    def replace(m):
        print(f'TEST REMOVE {m.span()}')
        return ''

    test = re.sub(pattern_re, replace, test)
    m = re.search(pattern_re, test)
    if m:
        print(f'TEST STILL THERE "{m.span()}"')

    Actual output:

    TEST FOUND "(10, 19)"
    TEST STILL THERE "(10, 19)"
    COMPILE PATTERN FIRST
    TEST FOUND "(10, 19)"
    TEST REMOVE (10, 19)

    This is an inconsistency between re.search and re.sub. Either this is a bug in the code or in the documentation.

  2. jlaurens
    added
    3.8 (EOL)end of life
    topic-IO
    type-bugAn unexpected behavior, bug, or error
    on Nov 26, 2020

  3. mrabarnett commented on Nov 26, 2020

    @mrabarnett
    mrabarnettmannequin
    on Nov 26, 2020
    Mannequin

    Not a bug.

    Argument 4 of re.sub is the count:

        sub(pattern, repl, string, count=0, flags=0)

    not the flags.

  4. mrabarnett
    closed this as completedon Nov 26, 2020
  5. mrabarnett
    added
    invalid
    on Nov 26, 2020
  6. mrabarnett
    closed this as completedon Nov 26, 2020
  7. mrabarnett
    added
    invalid
    on Nov 26, 2020
  8. ezio-melotti
    transferred this issue fromon Apr 10, 2022
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