Define and use Modules

# Fibonacci numbers module

#//File: fibo.py
def fib(n):    # write Fibonacci series up to n
    a, b = 0, 1
    while b < n:
        print b,
        a, b = b, a+b

def fib2(n): # return Fibonacci series up to n
    result = []
    a, b = 0, 1
    while b < n:
        result.append(b)
        a, b = b, a+b
    return result

import fibo

fibo.fib(1000)

fibo.fib2(100)

fibo.__name__
'fibo'

#//If you intend to use a function often you can assign it to a local name:

fib = fibo.fib
fib(500)