Overlapping matches in Regular Expressions

[André Søreng]

With the re/sre module included with Python 2.4:

pattern = "(?P<id1>avi)|(?P<id2>avi|mp3)"
string2match = "some string with avi in it"
matches = re.finditer(pattern, string2match)
....
matches[0].groupdict()
{'id2': None, 'id1': 'avi'}

Which was expected since overlapping matches are ignored.
But I would also like to know if other groups had a match.
What modifications to the re/sre module is needed to allow
overlapping matches?

[Fredrik Lundh]

André Søreng wrote:

With the re/sre module included with Python 2.4:

pattern = "(?P<id1>avi)|(?P<id2>avi|mp3)"
string2match = "some string with avi in it"
matches = re.finditer(pattern, string2match)
...
matches[0].groupdict()
{'id2': None, 'id1': 'avi'}

Which was expected since overlapping matches are ignored.
But I would also like to know if other groups had a match.
that's not how regular expressions work: a regular expression describes a
set of strings (the regular set), and the engine can tell you if a given string
belongs to that set.
What modifications to the re/sre module is needed to allow
overlapping matches?

if you want overlapping matches, you have to apply the pattern multiple
times. for trivial cases like your example, it's probably easier to create a
single pattern that matches all interesting cases, and use a dictionary (or
a number of sets) to do the rest.

</F>