# Python 3: Fibonacci series up to n >>> def fib(n): >>> a, b = 0, 1 >>> while a < n: >>> print(a, end=' ') >>> a, b = b, a+b >>> print() >>> fib(1000) 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 Functions Defined The core of extensible programming is defining functions. Python allows mandatory and optional arguments, keyword arguments, and even arbitrary argument lists. More about defining f