python - 为什么不能将 eval() 函数与私有(private)变量一起使用？

Question

我想知道为什么不能对私有(private)属性使用 eval() 函数。

class A:
    def __init__(self):
        __private = 5
        print(__private + 2)  # Prints '7'
        print(eval('__private + 2'))  # NameError: name '__private' is not defined

A()

Answer 1

这与名称修改有关，请参阅 documentation :

Notice that code passed to exec() or eval() does not consider theclassname of the invoking class to be the current class; this issimilar to the effect of the global statement, the effect of which islikewise restricted to code that is byte-compiled together. The same restriction applies to getattr(), setattr() and delattr(), as well as when referencing __dict__ directly.

因此，要在 eval() 中正确使用私有(private)变量，它必须以经过修饰的形式传递，例如print(eval('_A__private + 2'))