Is there a command that returns the number of substrings in a string?

Gerard Flanagan grflanagan at gmail.com
Mon Oct 26 11:46:28 CET 2009


Peng Yu wrote:
> For example, the long string is 'abcabc' and the given string is
> 'abc', then 'abc' appears 2 times in 'abcabc'. Currently, I am calling
> 'find()' multiple times to figure out how many times a given string
> appears in a long string. I'm wondering if there is a function in
> python which can directly return this information.

re.findall?

 >>> patt = re.compile('abc')
 >>> len(patt.findall('abcabc'))
2

For groups of non-overlapping substrings, tested only as far as you see:

8<----------------------------------------------------------------------

import re
from collections import defaultdict

def count(text, *args):
     """
     >>> ret = count('abcabc', 'abc')
     >>> ret['abc']
     2
     >>> ret = count('xabcxabcx', 'abc', 'x')
     >>> ret['abc']
     2
     >>> ret['x']
     3
     >>> ret = count('abcabc', 'abc', 'cab')
     >>> ret['abc']
     2
     >>> ret['cab']
     0
     >>> ret = count('abcabc', 'abc', 'ab')
     >>> ret['abc']
     2
     >>> ret['ab']
     0
     """
     args = map(re.escape, args)
     args.sort()
     args.reverse()
     pattern = re.compile('|'.join(args))
     result = defaultdict(int)
     def callback(match):
         matched = match.group(0)
         result[matched] += 1
         return matched
     pattern.sub(callback, text)
     return result


if __name__ == '__main__':
     import doctest
     doctest.testmod()
8<----------------------------------------------------------------------




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