def function_name(param1, param2):
    ‘this is document‘
    pass # fuction body
    return value # 可选

>>> def print_params(*params):
...     print params
...
>>> print_params(1,2,3,4)
(1, 2, 3, 4)
>>>
>>> a=(1, 2, 3, 4)
>>> print_params(*a)
(1, 2, 3, 4)
>>> print_params(a)
((1, 2, 3, 4),)

def print_params_3(**params): 
    print params    
>>>
>>> print_params_3(a=1, b=2, c=3, d=4)
{‘a‘: 1, ‘c‘: 3, ‘b‘: 2, ‘d‘: 4}
>>>
>>> print_params_3(**a)
{‘a‘: 1, ‘c‘: 3, ‘b‘: 2, ‘d‘: 4}
>>> 

>>> def interval(start, stop=None, step=1):
...     ‘imitates range for step > 0‘
...     if stop == None:
...             start,stop=0,start
...     result=[]
...     i = start
...     while i < stop:
...             result.append(i)
...             i+=step
...     return result
...
>>>
>>> interval(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> interval(2,5)
[2, 3, 4]
>>>