在Python 3中的地图中调用none

Question

我在Python2.7中执行以下操作:

>>> a = [1,2,3,4,5]
>>> b = [2,1,3,4]
>>> c = [3,4]
>>> map(None, a, b, c)
[(1, 2, 3), (2, 1, 4), (3, 3, None), (4, 4, None), (5, None, None)]

我试图在Python3中做类似的事情

>>> a = [1,2,3,4,5]
>>> b = [2,1,3,4]
>>> c = [3,4]
>>> map(None, a, b, c)
<map object at 0xb72289ec>
>>> for i,j,k in map(None, a, b, c):
...  print (i,j,k)
... 
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not callable

如何在Python3中复制Python2结果？

Answer 1

请改用此itertools.zip_longest()功能:

from itertools import zip_longest

for i, j, k in zip_longest(a, b, c):

这将三个列表压缩在一起,用fillvalue关键字值填充(默认为None).