unicode string equivalent of contain

I have an error when trying to use contain in python.

s = u"some utf8 words"
k = u"one utf8 word"

if s.contains(k):
    print "contains" 

How do i achieve the same result?

Example with normal ASCII string

s = "haha i am going home"
k = "haha"

if s.contains(k):
    print "contains"

I am using python 2.7.x