New submission from Alexander Schmolck <[email protected]>:
In certain cases a zero-width /Z match that should be replaced isn't.
An example might help:
re.compile('(?m)(?P<trailing_ws>[
\t]+\r*$)|(?P<no_final_newline>(?<=[^\n])\Z)').subn(lambda m:next('<'+k+'>' for
k,v in m.groupdict().items() if v is not None), 'foobar ')
this gives
('foobar<trailing_ws>', 1)
I would have expected
('foobar<trailing_ws><no_final_newline>', 2)
Contrast this with the following behavior:
[m.span() for m in re.compile('(?P<trailing_ws>[
\t]+\r*$)|(?P<no_final_newline>(?<=[^\n])\Z)', re.M).finditer('foobar ')]
gives
[(6, 7), (7, 7)]
The matches are clearly not overlapping and the re module docs for sub say
"Return the string obtained by replacing the leftmost non-overlapping
occurrences of pattern in string by the replacement repl.", so I would have
expected two replacements.
This seems to be what perl is doing:
echo -n 'foobar ' | perl -pe 's/(?m)(?P<trailing_ws>[
\t]+\r*$)|(?P<no_final_newline>(?<=[^\n])\Z)/<$&>/g'
gives
foobar< ><>%
----------
components: Regular Expressions
messages: 120499
nosy: Alexander.Schmolck
priority: normal
severity: normal
status: open
title: re.sub[n] doesn't seem to handle /Z replacements correctly in all cases
type: behavior
versions: Python 2.6, Python 3.1
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Python tracker <[email protected]>
<http://bugs.python.org/issue10328>
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