re.I does not work as expected

[MageshKumar]

BPO	26354
Nosy	@ezio-melotti
Superseder	bpo-11957: re.sub confusion between count and flags args

^{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 2016-02-13.00:44:14.426>
created_at = <Date 2016-02-13.00:19:24.626>
labels = ['expert-regex', 'type-bug', 'invalid']
title = 're.I does not work as expected'
updated_at = <Date 2016-02-15.22:11:04.050>
user = 'https://bugs.python.org/MageshKumar'

bugs.python.org fields:

activity = <Date 2016-02-15.22:11:04.050>
actor = 'Magesh Kumar'
assignee = 'none'
closed = True
closed_date = <Date 2016-02-13.00:44:14.426>
closer = 'ezio.melotti'
components = ['Regular Expressions']
creation = <Date 2016-02-13.00:19:24.626>
creator = 'Magesh Kumar'
dependencies = []
files = []
hgrepos = []
issue_num = 26354
keywords = []
message_count = 9.0
messages = ['260216', '260219', '260220', '260328', '260329', '260330', '260331', '260334', '260335']
nosy_count = 3.0
nosy_names = ['ezio.melotti', 'mrabarnett', 'Magesh Kumar']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = '11957'
type = 'behavior'
url = 'https://bugs.python.org/issue26354'
versions = ['Python 2.7']

[MageshKumar]

I am in the process of re.sub the tag <item type="dict"> </item> with empty string from a xml output line.

If "re.I" is used, I am not able to remove the complete tag.

========================================================================

>>> a
'ype="str">false</latency_statistics_enabled><name type="str">Default</name><aggregates type="list"><item type="dict"><aggregate type="list"><item type="dict"><type type="str">MulticastClient</item><is'

>>> b = re.sub('\<\/?item(\s+type="dict")?\>', '', a, re.I)
>>> b
'ype="str">false</latency_statistics_enabled><name type="str">Default</name><aggregates type="list"><aggregate type="list"><type type="str">MulticastClient</item><is'
>>> b = re.sub('\<\/?item(\s+type="dict")?\>', '', a)
>>> b
'ype="str">false</latency_statistics_enabled><name type="str">Default</name><aggregates type="list"><aggregate type="list"><type type="str">MulticastClient<is'

========================================================================

[mrabarnett]

The 4th argument of re.sub is the count, not the flags.

Not a bug.

[ezio-melotti]

See bpo-11957

[MageshKumar]

Thanks for the inputs, It would be of great help, if someone could help me in explaining the below output :
========================================================================

>>> a 
'ype="str">false</latency_statistics_enabled><name type="str">Default</name><aggregates type="list"><item type="dict"><aggregate type="list"><root><type type="str">MulticastClient</root><is'
>>> b = re.sub('\</?root\>', '', a, re.I)
>>> b
'ype="str">false</latency_statistics_enabled><name type="str">Default</name><aggregates type="list"><item type="dict"><aggregate type="list"><type type="str">MulticastClient<is'

========================================================================

[mrabarnett]

The pattern '\</?root\>', which is the same as '</?root>', matches the string '<root>', and that is replaced with ''.

[MageshKumar]

:-)
Thanks a lot Matthew for the inputs.

If we compare the first example (<item>) and the <root> example, I am using re.I as the third element. But for the <root> example, still I am not to get the substitution happening correctly.

Could you pls, let me know the reason of change in behaviour.

[MageshKumar]

Corrected Message :

If we compare the first example (<item>) and the <root> example, I am using re.I as the third element. But for the <root> example, still I am able to get the substitution happening correctly.

Could you pls, let me know the reason of change in behaviour.

[mrabarnett]

The 3rd argument is the count (the maximum number of replacements, although 0 means no limit, not no replacements). You're passing in the flag re.I instead. re.I happens to have the numeric value 2, so you're telling it to do no more than 2 replacements.

[MageshKumar]

Thanks Matthew. :-)