嵌套在函数和属性查找中的类

Question

以下工作正常,即它没有给出任何错误:

def foo(arg):
    class Nested(object):
        x = arg

foo('hello')

但以下引发异常:

def foo(arg):
    class Nested(object):
        arg = arg # note that names are the same

foo('hello')

追溯:

Traceback (most recent call last):
  File "test.py", line 6, in <module>
    foo('hello')
  File "test.py", line 3, in foo
    class Nested(object):
  File "test.py", line 4, in Nested
    arg = arg
NameError: name 'arg' is not defined

我无法理解这种行为的原因.有人可以解释一下吗？

Answer 1

该arg属性隐藏了arg函数参数(内部范围)

def foo(arg):
    class Nested(object):
        arg = arg # you try to read the `arg` property which isn't initialized

如果i = i在没有初始化i变量的情况下键入解释器窗口,则会出现相同的错误 .