Python regex: overlapping patterns

Question

Suppose I have a string:

string = 'AvBvC'

I want to match A, B, and C, and this is what I did:

match = re.search('(.*)v(.*)', string)
print match.groups()

The problem is, the result shows that:

('AvB', 'C',)

instead of what I want, which is

('A', 'B', 'C',)

How do I make it catch all overlapping patterns..?

Thanks.

(I know there are some posts concerning the same issue, but haven't found a definite answer for Python)

@PeterDeGlopper Yeah!! just modified my post (my original code is way longer and more complicated than this,, sorry) — user2492270
– user2492270, Commented Dec 8, 2013 at 4:04
More details would help - you can do what the above question asks with just split('v'), so I can only assume you have a more complicated situation. — Peter DeGlopper
– Peter DeGlopper, Commented Dec 8, 2013 at 4:06
This may be what you are after? stackoverflow.com/questions/5616822/… — OllyTheNinja
– OllyTheNinja, Commented Dec 8, 2013 at 4:06

FogleBird · Accepted Answer · 2013-12-08 04:37:39Z

2

Use re.split

>>> import re
>>> re.split('v', 'AvBvC')
['A', 'B', 'C']

And to demonstrate further...

>>> re.split('vw', 'AAvwBBvwCC')
['AA', 'BB', 'CC']

answered Dec 8, 2013 at 4:37

FogleBird

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Comments

hwnd · Accepted Answer · 2013-12-08 04:43:42Z

2

Your question is somewhat unclear, you seem to have more of a complicated string than you actual show.

Using search() matches only the first occurrence, you can use findall() to match all occurrences.

matches = re.findall(r'[^v]+', string)
['A', 'B', 'C']

Another option would be to split on certain characters that you need to split on.

>>> re.split('v', 'AvBvC')
['A', 'B', 'C']

edited Dec 8, 2013 at 4:43

answered Dec 8, 2013 at 4:03

hwnd

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10 Comments

user2492270 Over a year ago

This works for my example, but my actual string contains things that are not single character such as A,B,C... So is there a way to do this while using "search" instead of "findall"??

Tim Peters Over a year ago

search() and match() return exactly 1 result. So, no. You need to make your question clearer ;-)

thefourtheye Over a year ago

@TimPeters Why negative lookahead doesnt allow me to match beginning of the string?

Tim Peters Over a year ago

@thefourtheye, huh? Without some context (or code), I don't know what you're asking - sorry.

Tim Peters Over a year ago

@thefourtheye, then some people are bound to get confused by sloppy terminology ;-) The "fixed width" restriction is unique to look-behinds - it does not apply to look-aheads. The reason is simply the sheer difficulty of implementing varying-width look-behinds; they're "highly unnatural" for a "left to right" search engine.

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