用Python编写循环的方法 [英] Pythonic way to write a loop

问题描述

我有两个列表:a = [1, 2, 3]和b = [4, 5, 6].

我在python中使用了两个循环，从a的每个元素中减去b的每个元素.

I have used two loops in python to subtract each element of b from each element of a.

import numpy as np
a = [1, 2, 3]
b = [4, 5, 6]
p = -1
result = np.zeros(len(a)*len(a))
for i in range(0,len(a)):
    for j in range(0,len(a)):
        p = p + 1
        result[p] = a[i] - b[j]

我的结果是正确的:result = [-3., -4., -5., -2., -3., -4., -1., -2., -3.].

但是，我想知道是否还有更优雅的('pythonic')方法.

However, I would like to know if there is more elegant('pythonic') way to do it.

推荐答案

无需使用索引.您可以遍历这些值.

There is no need to use an index. You can iterate over the values.

a = [1, 2, 3]
b = [4, 5, 6]
result = []
for x in a:
    for y in b:
        result.append(x - y)

pythonic方式将是列表理解.

The pythonic way would be a list comprehension.

a = [1, 2, 3]
b = [4, 5, 6]
result = [x - y for x in a for y in b]

请记住，您应该在真实代码中为a，b，x和y使用有意义的名称.

Please bear in mind that you should use meaningful names for a, b, xand y in real code.

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