python find a string in another string

'''
    This code use for find one string in another string
    return the index from where string is found, otherwise return -1
'''
data="Life is very easy is with Python"

print data.find("is")
print data.rfind("is")
'''
   find in a range(startIndex,endIndex)
'''
print data.find("is",0,5)
print data.find("is",0,10)

'''
   find from last
'''
print data.rfind("is",0,10)
print data.rfind("is",0,5)

Output:

5
18
-1
5
5
-1