Question

I am trying to figure out how many times a string occurs in a string. For example:

nStr = '000123000123'

Say the string I want to find is 123. Obviously it occurs twice in nStr but I am having trouble implementing this logic into Python. What I have got at the moment:

pattern = '123'
count = a = 0
while pattern in nStr[a:]:
    a = nStr[a:].find(pattern)+1
    count += 1
return count

The answer it should return is 2. I’m stuck in an infinite loop at the moment.

I was just made aware that count is a much better way to do it but out of curiosity, does anyone see a way to do it similar to what I have already got?

Answer 1

Use str.count:

>>> nStr = '000123000123'
>>> nStr.count('123')
2

A working version of your code:

nStr = '000123000123'
pattern = '123'
count = 0
flag = True
start = 0

while flag:
    a = nStr.find(pattern, start)  # find() returns -1 if the word is not found, 
    #start i the starting index from the search starts(default value is 0)
    if a == -1:          #if pattern not found set flag to False
        flag = False
    else:               # if word is found increase count and set starting index to a+1
        count += 1        
        start = a + 1
print(count)