python regex: How can I have pattern searching for multiple pattern strings?

Question

I have to search the following patterns in a file, (any match qualifies)

pattern_strings = ['\xc2d', '\xa0', '\xe7', '\xc3\ufffdd', '\xc2\xa0', '\xc3\xa7', '\xa0\xa0', '\xc2', '\xe9']
pattern = [re.compile(x) for x in pattern_strings]

and function using this

def find_pattern(path):
    with open(path, 'r') as f:
        for line in f:
            found = pattern.search(line)
            if found:
                logging.info('found - ' + found)

When I try using it

find_pattern('myfile')

I see AttributeError: "'list' object has no attribute 'search'"

because patterns is

[<_sre.SRE_Pattern object at 0x107948378>, <_sre.SRE_Pattern object at 0x107b31c70>, <_sre.SRE_Pattern object at 0x107b31ce0>, <_sre.SRE_Pattern object at 0x107ac3cb0>, <_sre.SRE_Pattern object at 0x107b747b0>, <_sre.SRE_Pattern object at 0x107b74828>, <_sre.SRE_Pattern object at 0x107b748a0>, <_sre.SRE_Pattern object at 0x107b31d50>, <_sre.SRE_Pattern object at 0x107b31dc0>]

How can I have one pattern which looks for all strings in pattern_strings?

Daniel DiPaolo · Accepted Answer · 2012-07-27 18:10:32Z

4

You could simply concatenate all the expressions together with a |:

pattern_strings = ['\xc2d', '\xa0', '\xe7', '\xc3\ufffdd', '\xc2\xa0', '\xc3\xa7', '\xa0\xa0', '\xc2', '\xe9']
pattern_string = '|'.join(pattern_strings)
pattern = re.compile(pattern_string)

This does, however, assume that none of your patterns are complicated enough that a simple concatenation like this might break. For the ones in your example, it should work. For more complex patterns, it may not.

answered Jul 27, 2012 at 18:10

Daniel DiPaolo

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1 Comment

Joran Beasley Over a year ago

you should also sort the list longest to shortest... otherwise you will get not the results you expect..

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