how to check if a word in a sentence contains a letter in python code example

Example 1: if substring not in string python

fullstring = "StackAbuse"
substring = "tack"

if fullstring.find(substring) != -1:
    print "Found!"
else:
    print "Not found!"

Example 2: how to check if a string contains a word python

if word in mystring: 
   print('success')