Counting all permutations of a substring

[mensanator at aol.com]

Chris Lasher wrote:
> Hi all,
> How can one count all the permutations of a substring in a string? For
> a more concrete example, let's say
> targetstr = 'AAA'
> and
> probestr = 'AA'
>
> I want to consider how many times one can count probestr ('AA') in
> targetstr ('AAA'). The value in this example is, obviously, 2: you can
> match the first and second A's as 'AA' and also the second and third
> A's as 'AA'. Compiling a regular expression of the probestr and doing a
> findall(targetstr) will not work because the RE stops on the first
> combination of 'AA' that it finds (the first and second A's of the
> targetstr). The regular expression re.compile(r'A{2,}'} will not work,
> either; it simply consumes all three A's as one match. The string
> method count('AA') acts similarly to the findall of the 'AA' RE,
> returning 1, as it only matches the first and second A's.
>
> Any suggestions on how to get at that 2nd pair of A's and count it?
> Humbly, I'm a bit stumped. Any help would be appreciated.

>>> def ss(a,b):
	matches = 0
	lc = len(a)-len(b)+1
	for i in xrange(lc):
		if a[i:i+lb]==b:
			print a
			print ' '*i+b
			print
			matches += 1
	return matches

>>> ss('AAABCDEAAAAABSAABAWA','AA')
AAABCDEAAAAABSAABAWA
AA

AAABCDEAAAAABSAABAWA
 AA

AAABCDEAAAAABSAABAWA
       AA

AAABCDEAAAAABSAABAWA
        AA

AAABCDEAAAAABSAABAWA
         AA

AAABCDEAAAAABSAABAWA
          AA

AAABCDEAAAAABSAABAWA
              AA

7



> 
> Many thanks in advance,
> Chris