Searching list of strings using regular expressions in python

Question

I have a list of Strings. I want to select the strings which match a certain pattern using regular expression. Python regular expressions dont take a list and I dont want to use loops.

Any suggestion?

Why don't you want to use loops? You seem to know the basics of how to approach this, but are stating that it's a constraint that you can't... So.... errr? Would filter suffice? — Jon Clements
– Jon Clements, Commented Nov 10, 2013 at 0:40
loops are very slow... really? Premature optimisation and all that... — Jon Clements
– Jon Clements, Commented Nov 10, 2013 at 0:42

Tim Peters · Accepted Answer · 2013-11-10 00:48:40Z

2

Try:

def searcher(s):
    if COMPILED_REGEXP_OBJECT.search(s):
        return s

matching_strings = filter(searcher, YOUR_LIST_OF_STRING)

searcher() returns the string if it matches, else returns None. filter() only returns "true" objects, so will skip the Nones. It will also skip empty strings, but doubt that's a problem.

Or, better, as @JonClements pointed out:

matching_strings = filter(COMPILED_REGEXP_OBJECT.search, YOUR_LIST_OF_STRING)

Not only shorter, it only looks up the .search method once (instead of once per string).

answered Nov 10, 2013 at 0:48

Tim Peters

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