python3的zip函数

zip函数接受任意多个可迭代对象作为参数,将对象中对应的元素打包成一个tuple,然后返回一个可迭代的zip对象.

这个可迭代对象可以使用循环的方式列出其元素

若多个可迭代对象的长度不一致,则所返回的列表与长度最短的可迭代对象相同.

用法1:用两个列表生成一个zip对象

例1

>>> a1=[1,2,3]
>>> a2=[4,5,6]
>>> a3=[7,8,9]
>>> a4=["a","b","c","d"]
>>> zip1=zip(a1,a2,a3)
>>> print(zip1)
<zip object at 0x7f5a22651c08>
>>> for i in zip1:
...     print(i)
...
(1, 4, 7)
(2, 5, 8)
(3, 6, 9)

例2

>>> zip2=zip(a1,a2,a4)
>>> print(zip2)
<zip object at 0x7f5a22651d48>
>>> for j in zip2:
...     print(j)
...
(1, 4, 'a')
(2, 5, 'b')
(3, 6, 'c')

例3

>>> zip3=zip(a4)
>>> print(zip3)
<zip object at 0x7f5a22651d08>
>>> for i in zip3:
...     print(i)
...
('a',)
('b',)
('c',)
('d',)

例4

>>> zip4=zip(*a4 *3)
>>>
>>> print(zip4)
<zip object at 0x7f5a22651f08>
>>> for j in zip4:
...     print(j)
...
('a', 'b', 'c', 'd', 'a', 'b', 'c', 'd', 'a', 'b', 'c', 'd')

用法2:二维矩阵变换(矩阵的行列互换)

>>> l1=[[1,2,3],[4,5,6],[7,8,9]]
>>> print([[j[i] for j in l1] for i in range(len(l1[0])) ])
[[1, 4, 7], [2, 5, 8], [3, 6, 9]]
>>> zip(*l1)
<zip object at 0x7f5a22651f88>
>>> for i in zip(*l1):
...     print(i)
...
(1, 4, 7)
(2, 5, 8)
(3, 6, 9)