python的*args是什么意思？

niexining

1. from itertools import izip_longest
   
2. def grouper(n, iterable, fillvalue=None):
   
3.     "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
   
4.     args = [iter(iterable)] * n
   
5.     return izip_longest(fillvalue=fillvalue, *args)
   
6. for i in grouper(3,'ABCEDFG','x'): print i
   
7. 
   

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windows系統(tǒng)python2.7自帶文檔庫函數(shù)手冊中，有這樣一個例子。

請問*args是怎么用的？ izip_longest的參數(shù)一般有兩個，一個是迭代對象(iterable)，另一個是填充(filvalue)。為什么在這個例子中，參數(shù)卻是fillvalue和*args。

另外，某天有朋友問: 如何把列表3個3個地分組？     這兒似乎對這個問題提供了一種別樣的解答。

cdtits

貌似指明為元組

niexining

1. ('A', 'B', 'C')
   
2. ('E', 'D', 'F')
   
3. ('G', 'x', 'x')

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這是運行結(jié)果.


是不是放了3個迭代器進去, 就3個字符3個字符地迭代?

anonymous0502

4.7.4. Unpacking Argument Lists
The reverse situation occurs when the arguments are already in a list or tuple but need to be unpacked for a function call requiring separate positional arguments. For instance, the built-in range() function expects separate start and stop arguments. If they are not available separately, write the function call with the *-operator to unpack the arguments out of a list or tuple:

>>>
>>> range(3, 6)             # normal call with separate arguments
[3, 4, 5]
>>> args = [3, 6]
>>> range(*args)            # call with arguments unpacked from a list
[3, 4, 5]
In the same fashion, dictionaries can deliver keyword arguments with the **-operator:

>>>
>>> def parrot(voltage, state='a stiff', action='voom'):
...     print "-- This parrot wouldn't", action,
...     print "if you put", voltage, "volts through it.",
...     print "E's", state, "!"
...
>>> d = {"voltage": "four million", "state": "bleedin' demised", "action": "VOOM"}
>>> parrot(**d)
-- This parrot wouldn't VOOM if you put four million volts through it. E's bleedin' demised !

                           

niexining

回復 4# anonymous0502

這個兩個例子很好.   剩下的就是關(guān)于迭代器的還太理解.