Using RE to retrive an ID

Question

Hello, I am trying to use RE to match a changing ID and extract it. I am having some bother getting it working. The String is:

m = 'Some Text That exists version 1.0.41.476 Fri Jun  4 16:50:56 EDT 2010'

The code I have tried so far is:

r = re.compile(r'(s*\s*)(\S+)')
m = m.match(r)

Can anyone help extract this string.

Thanks

Answer 1

>>> m = 'Some Text That exists version 1.0.41.476 Fri Jun  4 16:50:56 EDT 2010'
>>> import re
>>> re.search(r'version (\S+)', m).group(1)
('1.0.41.476',)

Answer 2

You don't necessarily have to use a regular expression to extract a substring.

def get_version_number(text):
    """Assumes that the word 'version' appears before the version number in the 
    text."""
    words = text.split()
    index = words.index('version') + 1
    return words[index]

if __name__ == '__main__':
    m = 'Some Text That exists version 1.0.41.476 Fri Jun  4 16:50:56 EDT 2010'

    print get_version_number(m)
    print repr(get_version_number(m))

Answer 3

Here are RE-based and string-based versions:

import re

def bystr(text):
    words = text.split()
    index = words.index('version') + 1
    return words[index]

def byre(text, there=re.compile(r'version\s+(\S+)')):
    return there.search(text).group(1)

m = 'Some Text That exists version 1.0.41.476 Fri Jun  4 16:50:56 EDT 2010'

if __name__ == '__main__':
    print bystr(m)
    print byre(m)

(run as main script to confirm they return the same result -- a string, not a tuple as an existing answer peculiarly shows), and here's the timing of each (on my slow laptop):

$ python -mtimeit -s'import are' 'are.bystr(are.m)'
100000 loops, best of 3: 4.29 usec per loop
$ python -mtimeit -s'import are' 'are.byre(are.m)'
100000 loops, best of 3: 3.25 usec per loop

While RE often have a bad reputation in the Python community, even this simple example shows that, when appropriate, they can often be faster than simple string manipulation -- in this case, the RE version takes only about 3/4 of the time that the string version takes.