def count_substring(string, sub_string):
		count = 0
    str1 = ''
    for i in range(len(string)):
        str1 = str1 + string[i]
        if len(str1) == len(sub_string)+1:
            str1 = str1[ 1 : len(sub_string)+1 ]   
        if str1 == sub_string:
            count +=1
        
    return count

def count_substring(string, sub_string):
    count = 0
    for i in range(len(string) - len(sub_string) + 1):
# string.find returns -1 if false, but some other value if true. 
        if string.find(sub_string, i, len(sub_string)+i) != -1:
            count += 1
    return count

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

def count_substring(string, sub_string):
    count = 0;
    str_len = len(string)
    sub_len = len(sub_string)
    i=0
    while i< (str_len-sub_len+1):
        index = string.find(sub_string, i)
        if index != -1:
            count = count + 1 
            i = index   
        i = i+1
        
    return count