Extra output none while printing an command line argument

It's my day 1 of learning python. so it's a noob question for many of you. See the following code:

#!/usr/bin/env python

import sys

def hello(name):
    name = name + '!!!!'
    print 'hello', name

def main():
    print hello(sys.argv[1])


if __name__ == '__main__':
    main()

when I run it

$ ./Python-1.py alice
hello alice!!!!
None

Now, I have trouble understanding where this "None" came from?