Number of occurance

def count_substring(string, sub_string):
    count=0
    sublength = len(sub_string)
    for i in range(len(string)):
        try:
            st = 0
            st = string.index(sub_string,i,sublength+i)
            if(st>0):
                #print("Caught",i,sublength+i)
                count = count+1
        except:
            #print("Error")
            continue
          
    return count