python - 有人可以向我解释函数对象和闭包之间的区别吗

Question

“函数对象”是指某个类的对象，它在某种意义上是可调用的，并且可以在语言中被视为函数。例如，在 python 中:

class FunctionFactory:
    def __init__ (self, function_state):
        self.function_state = function_state
    def __call__ (self):
        self.function_state += 1
        return self.function_state

>>>> function = FunctionFactory (5)
>>>> function ()
6
>>>> function ()
7

我的问题是 - 这种对 FunctionFactory 和 function 的使用会被视为闭包吗？

Answer 1

闭包是一个函数，它会记住定义它的环境并且可以访问周围范围内的变量。函数对象是可以像函数一样调用的对象，但实际上可能不是函数。函数对象不是闭包:

class FunctionObject(object):
    def __call__(self):
        return foo

def f():
    foo = 3
    FunctionObject()() # raises UnboundLocalError

FunctionObject 无权访问创建它的范围。但是，函数对象的 __call__ 方法可能是一个闭包:

def f():
    foo = 3
    class FunctionObject(object):
        def __call__(self):
            return foo
    return FunctionObject()
print f()() # prints 3, since __call__ has access to the scope where it was defined,
            # though it doesn't have access to the scope where the FunctionObject
            # was created