counting a collection of letters within a string

[blackpaddycat]

Hi
I am trying to write code that will return all instances of a collection of letters in a string variable...
I can get a count returned, but it does not cater for letters that are used twice... for example

s = 'ajsfhbababnsnbabnndbab'
n = s .count (str('bab'))
print 'Number of times bab occurs is: ' + str(n)

The code returns 3 instances but actually it is 4 - it is not counting the babab as 2 instances.

Any suggestions gratefully received!
Thanks!

[dwblas]

You have to create your own code when builtins assume things you don't want.

s = 'ajsfhbababnsnbabnndbab'
found=0
location = -1
while True:
    location = s.find("bab", location+1)
    if location > -1:
        found += 1
    else:
        break

print 'Number of times bab occurs is: %s' % (found)

[bvdet]

Create your own count function using string slice. Example:

>>> def count_str(s, find_str):
... 	count = 0
... 	for i in range(len(s)):
... 		if s[i:i+len(find_str)] == find_str:
... 			count += 1
... 	return count
... 
>>> s = 'ajsfhbababnsnbabnndbab'
>>> count_str(s, "bab")
4
>>>

[bvdet]

Here's the function in my previous post as a list comprehension:

>>> s = 'ajsfhbababnsnbabnndbab'
>>> find_str = "bab"
>>> [s[i:i+len(find_str)] == find_str for i in range(len(s))].count(True)
4
>>>