matching exactly a 4 digit number in python

[skip at pobox.com]

    >> I am a few months new into python. I have used regexps before in perl
    >> and java but am a little confused with this problem.

    >> I want to parse a number of strings and extract only those that
    >> contain a 4 digit number anywhere inside a string

    >> However the regexp
    >> p = re.compile(r'\d{4}')

    >> Matches even sentences that have longer than 4 numbers inside strings
    >> ..for example it matches "I have 3324234 and more"

Try this instead:

    >>> pat = re.compile(r"(?<!\d)(\d{4})(?!\d)")>>> for s in x:
    ...   m = pat.search(s)
    ...   print repr(s),
    ...   print (m is not None) and "matches" or "does not match"
    ... 
    ' I have 2004 rupees ' matches
    ' I have 3324234 and more' does not match
    ' As 3233 ' matches
    '2323423414 is good' does not match
    '4444 dc sav 2412441 asdf ' matches
    'random1341also and also' matches
    '' does not match
    '13' does not match
    ' a 1331 saves' matches
    ' and and as dad' does not match
    ' A has 13123123' does not match
    'A  13123' does not match
    '123 adn' does not match
    '1312 times I have told you' matches

-- 
Skip Montanaro - skip at pobox.com - http://smontanaro.dyndns.org/