Python NameError：名称'N'未定义[重复]

为什么在使用类变量时Python（3.8）会抛出NameError？以下工作正常，

class Tester(object):
    # Number of measurements
    N = 6
    temp = [ 0. for x in range(N) ]

但是，当我尝试如下使用它时，它给出了NameError。

class Tester(object):
    # Number of measurements
    N = 6
    temp = [[ 0. for x in range(N) ] for y in range(N) ]

It seems to be happening for the first N. So something like temp = [[ 0. for x in range(6) ] for y in range(N) ] works fine.

When I replace N by Tester.N, it gives NameError for Tester, which makes sense since the class is not defined.

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