Re: Is there a command that returns the number of substrings in a string?
alex23 wrote: Gerard Flanagan grflana...@gmail.com wrote: def count(text, *args): Other than the ability to handle multiple substrings, you do realise you've effectively duplicated str.count()? I realise that calling this count function with a single argument would be functionally identical to calling str.count(), yes. But I can imagine the situation of wanting to find multiple (disjoint) substrings. Is there a reason for preferring multiple calls to str.count() in such a case? Or is there a more obvious approach? Gerard Flanagan grflana...@gmail.com wrote: re.findall? Forget that, that was stupid. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a command that returns the number of substrings in a string?
En Tue, 27 Oct 2009 04:31:22 -0300, Gerard Flanagan grflana...@gmail.com escribió: alex23 wrote: Gerard Flanagan grflana...@gmail.com wrote: def count(text, *args): Other than the ability to handle multiple substrings, you do realise you've effectively duplicated str.count()? I realise that calling this count function with a single argument would be functionally identical to calling str.count(), yes. But I can imagine the situation of wanting to find multiple (disjoint) substrings. Is there a reason for preferring multiple calls to str.count() in such a case? Or is there a more obvious approach? There is a more efficient algorithm (Aho-Corasick) which computes all occurences of a set of substrings inside a given string at once. It *should* be faster than repeatly calling str.find for every substring, and faster than using regular expressions too. (note that you get not only the count of occurences, but their positions too). I've seen a couple implementations for Python; if they're *actually* faster is to be determined... -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a command that returns the number of substrings in a string?
Gerard Flanagan grflana...@gmail.com wrote: I realise that calling this count function with a single argument would be functionally identical to calling str.count(), yes. But I can imagine the situation of wanting to find multiple (disjoint) substrings. Is there a reason for preferring multiple calls to str.count() in such a case? Or is there a more obvious approach? No, I totally missed that it was counting disjoint substrings :) -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a command that returns the number of substrings in a string?
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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Re: Is there a command that returns the number of substrings in a string?
Gerard Flanagan grflana...@gmail.com wrote: def count(text, *args): Other than the ability to handle multiple substrings, you do realise you've effectively duplicated str.count()? -- http://mail.python.org/mailman/listinfo/python-list
Is there a command that returns the number of substrings in a string?
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. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a command that returns the number of substrings in a string?
On Fri, Oct 23, 2009 at 7:31 PM, Peng Yu pengyu...@gmail.com 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.
'abcabc'.count('abc')
2
print ''.count.__doc__
S.count(sub[, start[, end]]) - int
Return the number of non-overlapping occurrences of substring sub in
string S[start:end]. Optional arguments start and end are interpreted
as in slice notation.
HTH,
--S
--
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Re: Is there a command that returns the number of substrings in a string?
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. The .count string method. -- Erik Max Francis m...@alcyone.com http://www.alcyone.com/max/ San Jose, CA, USA 37 18 N 121 57 W AIM/Y!M/Skype erikmaxfrancis Diplomacy and defense are not substitutes for one another. Either alone would fail. -- John F. Kennedy, 1917-1963 -- http://mail.python.org/mailman/listinfo/python-list
