How to determine whether a substring is in a different string

with in: substring in string:

>>> substring = "please help me out"
>>> string = "please help me out so that I could solve this"
>>> substring in string
True

foo = "blahblahblah"
bar = "somethingblahblahblahmeep"
if foo in bar:
    # do something

(By the way - try to not name a variable string, since there's a Python standard library with the same name. You might confuse people if you do that in a large project, so avoiding collisions like that is a good habit to get into.)

If you're looking for more than a True/False, you'd be best suited to use the re module, like:

import re
search="please help me out"
fullstring="please help me out so that I could solve this"
s = re.search(search,fullstring)
print(s.group())

s.group() will return the string "please help me out".