python - 你如何在 python 中进行长列表理解？

Question

例如:

>>> [x for x in range(y) for y in range(z) for z in range(3)]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'y' is not defined

我希望这与以下行为相同:

>>> a=[]
>>> for z in range(3):
...   for y in range(z):
...     for x in range(3):
...       a.append(x)
... 
>>> a
[0, 1, 2, 0, 1, 2, 0, 1, 2]

但事实并非如此。为什么？

Answer 1

如果您颠倒循环的顺序，您当前的理解将起作用:

[x for z in range(3) for y in range(z) for x in range(3)]