更新步骤后的python for循环？

Question

我从 this 复制了这段代码网站，我只是想知道这里的语法？为什么for循环在'i+1'下面？

# centroids[i] = [x, y]
centroids = {
    i+1: [np.random.randint(0, 80), np.random.randint(0, 80)]
    for i in range(k)
}

代码产生以下结果:

>>> np.random.seed(200)
>>> k = 3
>>> # centroids[i] = [x, y]
... centroids = {
...     i+1: [np.random.randint(0, 80), np.random.randint(0, 80)]
...     for i in range(k)
... }
>>>     
... 
>>> centroids
{1: [26, 16], 2: [68, 42], 3: [55, 76]}

Answer 1

这是一个字典理解(类似于列表理解)，但是括号让它看起来像是一个普通的字典初始化。

想象一下，如果括号在同一行:

centroids = {i+1: [np.random.randint(0, 80), np.random.randint(0, 80)] for i in range(k)}

所以这只是一种更冗长的说法:

centroids = {}
for i in range(k):
    centroids[i+1] = [np.random.randint(0, 80), np.random.randint(0, 80)]