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re.Scanner doesn't support more than 2 groups on regex #56998
Description
| BPO | 12789 |
|---|---|
| Nosy | @ezio-melotti |
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 2011-08-20.18:51:59.901>
created_at = <Date 2011-08-20.03:13:58.785>
labels = ['expert-regex', 'type-bug', 'invalid']
title = "re.Scanner doesn't support more than 2 groups on regex"
updated_at = <Date 2011-08-20.19:00:55.955>
user = 'https://bugs.python.org/angelonuffer'bugs.python.org fields:
activity = <Date 2011-08-20.19:00:55.955>
actor = 'ezio.melotti'
assignee = 'none'
closed = True
closed_date = <Date 2011-08-20.18:51:59.901>
closer = 'angelonuffer'
components = ['Regular Expressions']
creation = <Date 2011-08-20.03:13:58.785>
creator = 'angelonuffer'
dependencies = []
files = []
hgrepos = []
issue_num = 12789
keywords = []
message_count = 3.0
messages = ['142511', '142543', '142554']
nosy_count = 3.0
nosy_names = ['ezio.melotti', 'mrabarnett', 'angelonuffer']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue12789'
versions = ['Python 2.7']
Activity
angelonuffer commentedon Aug 20, 2011
When I use the scanner object in re module, I can create groups on regex and associate this to a method...
In [17]: re.Scanner([(r"(\w)(\w)\w", foo)])
Out[17]: <re.Scanner instance at 0x15c4e60>
But I tryed 3 groups and it raises "invalid SRE code", but I think my regex is not wrong...
In [15]: scan = re.Scanner([(r"(\w)(\w)(\w)", foo)])
---------------------------------------------------------------------------
/home/angelo/<ipython console> in <module>()
/usr/lib/python2.7/re.pyc in __init__(self, lexicon, flags)
305 s.groups = len(p)+1
306 p = sre_parse.SubPattern(s, [(BRANCH, (None, p))])
--> 307 self.scanner = sre_compile.compile(p)
308 def scan(self, string):
309 result = []
/usr/lib/python2.7/sre_compile.pyc in compile(p, flags)
520 return _sre.compile(
521 pattern, flags | p.pattern.flags, code,
522 p.pattern.groups-1,
--> 523 groupindex, indexgroup
524 )
RuntimeError: invalid SRE code
mrabarnett commentedon Aug 20, 2011
Even if this bug is fixed, it still won't work as you expect, and this s why.
The Scanner function accepts a list of 2-tuples. The first item of the tuple is a regex and the second is a function. For example:
The Scanner function then builds a regex, using the given regexes as alternatives, each wrapped as a capture group:
When matching, it sees which group captured and uses that to decide which function it should call, so, for example, if group 1 matched, it calls "number", and if group 2 matched, it calls "word".
When you introduce capture groups into the regexes, it gets confused. If your regex matches, it'll see that groups 1 and 2 match, so it'll try to call the second function, but there's isn't one...
[-]re.Scanner don't support more then 2 groups on regex[/-][+]re.Scanner doesn't support more than 2 groups on regex[/+]angelonuffer commentedon Aug 20, 2011
Ah, ok, thanks...
Then I think my idea is impossible.
I will use the Scanner in normal way. :)