count in python string

string.count(substring, start, end)
# Start and end is optional

def count_substring(string,sub_string):
    l=len(sub_string)
    count=0
    for i in range(len(string)-len(sub_string)+1):
        if(string[i:i+len(sub_string)] == sub_string ):      
            count+=1
    return count  

it counts the number of elements in the list or in the string(words)

string.count(substring, start=..., end=...)

'recede'.count('e')
>>> 3
'recede'.count('e', 2, 4)
>>> 1