在Python中修改闭包的绑定变量

Question

有没有办法修改闭包内部变量之一的绑定值？查看示例以更好地理解它。

def foo():
    var_a = 2
    var_b = 3

    def _closure(x):
        return var_a + var_b + x

    return _closure


localClosure = foo()

# Local closure is now "return 2 + 3 + x"
a = localClosure(1) # 2 + 3 + 1 == 6

# DO SOME MAGIC HERE TO TURN "var_a" of the closure into 0
# ...but what magic? Is this even possible?

# Local closure is now "return 0 + 3 + x"
b = localClosure(1) # 0 + 3 +1 == 4

Answer 1

我认为在Python中没有任何方法可以做到这一点。定义闭包后，将捕获封闭范围内变量的当前状态，并且不再具有可直接引用的名称（从闭包外部）。如果要foo()再次调用，则新的闭包将具有与封闭范围不同的变量集。

在简单的示例中，使用类可能会更好：

class foo:
        def __init__(self):
                self.var_a = 2
                self.var_b = 3

        def __call__(self, x):
                return self.var_a + self.var_b + x

localClosure = foo()

# Local closure is now "return 2 + 3 + x"
a = localClosure(1) # 2 + 3 + 1 == 6

# DO SOME MAGIC HERE TO TURN "var_a" of the closure into 0
# ...but what magic? Is this even possible?
localClosure.var_a = 0

# Local closure is now "return 0 + 3 + x"
b = localClosure(1) # 0 + 3 +1 == 4

如果您确实使用了这种技术，我将不再使用该名称，localClosure因为它实际上不再是一个闭包。但是，它的工作原理与以前相同。