Counting bobs

Assume s is a string of lower case characters.

Write a program that prints the number of times the string 'bob' occurs in s. For example, if s = 'azcbobobegghakl'
, then your program should print

Number of times bob occurs is: 2

s='azcbobobegghakl'
count = 0
while s:
    position = s.find('bob')
    if position!=-1:
        count+=1
    else:
        break
    s=s[position+1:]
print 'Number of times bob occurs is: '+str(count)