Defining functions in python


def fib(n):
  """Return a list of fibonacci numbers smaller than N"""
  a, b = 0, 1
  result = []
  while b < n:
    result.append(b)
    a, b = b, a+b
  return result

>>> fib(10)
[1, 1, 2, 3, 5, 8]

functions can have default arguments
functions can have variable number of arguments
functions can return complex data structures