如何并行迭代两个数组？ [复制]

我看起来能够并行迭代两个数组（或仅使用一个 for 循环）。

这是我尝试过的脚本...

#!/usr/bin/env python

list1 = [ 'one', 'two', 'three' ]
list2 = [ 'I', 'II', 'III', 'IV', 'V' ]

for word in list1:
    print word + " from list1"

for roman in list2:
    print roman + " from list2"

for ( word, roman ) in (list1 list2):
         if word:
                 print word + " from list1"

    if roman:
        print roman + " from list2"

但显然是不正确的，因为我收到语法错误：

  File "./twoarr.py", line 12
    for ( word, roman ) in (list1 list2):
                                      ^
SyntaxError: invalid syntax

我正在尝试获得如下所示的输出：

one from list1
I from list2
two from list1
II from list2
three from list1
III from list2
IV from list2
V from list2

要迭代多个列表，您可以使用内置函数zip。根据文档，此函数返回一个元组列表，其中第 i 个元组包含每个参数序列或可迭代对象中的第 i 个元素。因此，应用于您的特定示例

list1 = [ 'one', 'two', 'three' ]
list2 = [ 'I', 'II', 'III', 'IV', 'V' ]

for word in list1:
    print word + " from list1"

for roman in list2:
    print roman + " from list2"

for word, roman in zip(list1, list2):
    print word + " from list1"
    print roman + " from list2"
   

zip 的唯一缺点是，当您的列表（如此例中所示）长度不相等时，zip 将返回一个元组列表，每个元组的维度等于较小的元组。为了支持最长的一个，并在必要时填充 None，只需将 zip 替换为itertools.izip_longest:

from itertools import izip_longest

list1 = [ 'one', 'two', 'three' ]
list2 = [ 'I', 'II', 'III', 'IV', 'V' ]

for word in list1:
    print word + " from list1"

for roman in list2:
    print roman + " from list2"

for word, roman in izip_longest(list1, list2):
    print word + " from list1"
    print roman + " from list2"