Find count of sub_string in string

Question

Why is this giving output as 1 and not 2:

string = "ABCDCDC"
print(string.count("CDC"))

Also, since this is not working, how can I get 2 in this case?

Because `count` method doesn't take overlapping substrings into account. — Mazdak, Jul 30 '18 at 16:23
@Kasramvd okay, but then how do I count overlapping substrings? — Ank, Jul 30 '18 at 16:25
@user3483203 what's so bad about using `string` as a variable name? I'd be more worried about using `str` as a variable name, since that is a built-in function. — Joel, Jul 30 '18 at 17:25
@Joel `string` is a module https://docs.python.org/3/library/string.html — user3483203, Jul 30 '18 at 17:26

score 1 · Answer 1 · answered Jul 30 '18 at 16:26

1

You could use a regular expression to count overlapping substrings:

import re
string = "ABCDCDC"
print(len(re.findall('(?=CDC)', string))) # 2

answered Jul 30 '18 at 16:26

Mike Scotty

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score 0 · Accepted Answer · answered Jul 30 '18 at 16:27

0

Here is an algorithmic solution

string = "ABCDCDC"
sub_string = "CDC"

count = 0
for i in range(len(string)):
    if string[i:len(sub_string)+i] == sub_string:
        count += 1 
print count

answered Jul 30 '18 at 16:27

Kenan

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score 0 · Answer 3 · answered Jul 30 '18 at 16:27

0

import re
print([m.start() for m in re.finditer('(?=CDC)', 'ABCDCDC')])

This should find all potentially overlapping occurences

answered Jul 30 '18 at 16:27

Rushabh Mehta

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Md. Rezwanul Haque · Answer 4 · 2018-07-30T16:34:58.670

0

You can try this simple way:

def overlapping_count(string, seek):
    seek_len = len(seek)
    return sum(c == seek[0] and string[i:i + seek_len] == seek
                  for i, c in enumerate(string))
string = "ABCDCDC"
print(overlapping_count(string, "CDC"))

edited Jul 30 '18 at 16:34

answered Jul 30 '18 at 16:29

Md. Rezwanul Haque

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Find count of sub_string in string

4 Answers4