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I have a file with a list of names in strings like:

(John|Mary|Bob)(Anderson|Brooks|Cook)

I'm trying to use regular expressions to pull the data out in strings like:

John Anderson John Brooks John Cook Mary Anderson Mary Brooks Mary Cook Bob Anderson Bob Brooks Bob Cook

I'm fairly new at RegEx so any help would be aprreciated. Thanks

Dean Buchanan
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3 Answers3

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That's not something you can do with a regex. Regex engines match text, they can't do a cartesian product on them. Of course you can use a regex to get started. Let's see - in Python, I'd do

>>> import itertools
>>> import re
>>> s  = "(John|Mary|Bob)(Anderson|Brooks|Cook)"
>>> names = [name.split("|") for name in re.findall(r"\(([^()]*)\)", s)]
>>> names
[['John', 'Mary', 'Bob'], ['Anderson', 'Brooks', 'Cook']]
>>> [" ".join(item) for item in itertools.product(*names)]
['John Anderson', 'John Brooks', 'John Cook', 'Mary Anderson', 'Mary Brooks', 
 'Mary Cook', 'Bob Anderson', 'Bob Brooks', 'Bob Cook']
Tim Pietzcker
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It looks like your source file is in regular expression form already, so your problem is basically just generating strings matching that regular expression.

Look at this question for some suggestions: Reversing a regular expression in Python

Community
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couchand
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A regex alone cannot quite accomplish this. In general a regex engine is only going to match one specific place in your input (such as the first possible match)--or maybe none at all--so you need a loop to iterate until all the input is consumed or the pattern no longer matches.

The loop can be either explicit (like a while(true){}) or implicit as with Tim's example. You didn't say what language and/or tools you are using so it's difficult to be specific--regex support varies. In Tim's example, looping is implicitly provided by the split() and findall() method. Perl's split() provides an implicit loop, too.

Andy70109
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