myfile.py

def my_function():
    print "I am a function!"

def main():
    print "I am the main function"

if __name__=='__main__':
    print "I am being run as 'main'"
    
    # Try uncommenting this and see what happens.
    # Or change it to my_function()
    
    # main() 

secondfile.py

from myfile import *

print "I'm importing myfile."
my_function()