通常情况下，可变参数将在参数列表中的最后（含有默认参数的时候，默认参数在可变参数后面。另外，传入字典参数也在可变参数之后，因为字典参数也是一种可变参数）。
在可变参数后面的参数，只能以关键字实参的方式传递，而不能使用位置实参传递方式。
def concat(*args, sep="/"):
return sep.join(args)
print(concat("earth", "mars", "venus"))
print(concat("earth", "mars", "venus",sep="."))
结果为：
>>>
===========RESTART: D:/python/pythonLearning/KeywordArguments.py ===========
earth/mars/venus
earth.mars.venus
（5）需要字典类型的参数“**”
下面例子中**keywords代表传入字典类型的参数，而且*一定要在**之前。
def cheeseshop(kind, *arguments, **keywords):
print("--Do you have any", kind, "?")
print("--I'm sorry, we're all out of", kind)
for arg inarguments:
print(arg)
print("-" * 40)
keys =sorted(keywords.keys())
for kw in keys:
print(kw,":", keywords[kw])
可以这样调用
cheeseshop("Limburger", "It's very runny, sir.",
"It's really very, VERY runny, sir.",
shopkeeper="Michael Palin",
client="John Cleese",
sketch="Cheese Shop Sketch")
当然结果如下：
>>>
===========RESTART: D:/python/pythonLearning/KeywordArguments.py ===========
-- Do you haveany Limburger ?
-- I'm sorry,we're all out of Limburger
It's very runny,sir.
It's reallyvery, VERY runny, sir.
----------------------------------------
client : JohnCleese
shopkeeper :Michael Palin
sketch : CheeseShop Sketch
（6）Unpacking Argument Lists（python3.6帮助文档上用的这个词，必应翻译给的翻译是开箱的参数列表，我感觉应该是参数列表的拆包，不够下面还是用了开箱这个词，大家理解下）
这是与之前把数据组合成list相反的操作，即把list中的数据进行开箱操作，把里面的数据全部取出来使用，有点不好理解，看个例子吧
>>> list(range(3,6))
[3, 4, 5]
>>> args=[3,6]
>>> list(range(*args))
[3, 4, 5]
>>> args=(3,6)
>>> list(range(*args))
[3, 4, 5]
>>>这里把args中的数据进行开箱操作,把里面的数据作为range的参数列表.很显然,这个开箱操作对于元组也是适用的.
另外,也可以对字典执行开箱操作,需要的是两个*号即可.
def parrot(voltage, state='a stiff',action='voom'):
print("-- This parrot wouldn't", action, end=' ')
print("if you put", voltage, "volts through it.",end=' ')
print("E's", state, "!")
d = {"voltage": "fourmillion", "state": "bleedin' demised","action": "VOOM"}
parrot(**d)
结果为:
>>>
=========== RESTART:D:/python/pythonLearning/KeywordArguments.py ===========
-- This parrot wouldn't VOOM if you putfour million volts through it. E's bleedin' demised !
>>>