Python:如何拦截一个不存在的方法调用？

Question

我想创建一个类,它不会Attribute Error对任何可能存在或不存在的方法进行调用:

我的课:

class magic_class:
    ...
    # How to over-ride method calls
    ...

预期产出:

ob = magic_class()
ob.unknown_method()
# Prints 'unknown_method' was called

ob.unknown_method2()
# Prints 'unknown_method2' was called

现在,unknown_method并unknown_method2没有实际存在于类中,但是如何在python中拦截方法调用？

Answer 1

覆盖__getattr__()魔法:

class MagicClass(object):
    def __getattr__(self, name):
        def wrapper(*args, **kwargs):
            print "'%s' was called" % name
        return wrapper

ob = MagicClass()
ob.unknown_method()
ob.unknown_method2()

版画

'unknown_method' was called
'unknown_method2' was called

Answer 2

以防万一有人试图将未知方法委托给对象，代码如下：

class MagicClass():
    def __init__(self, obj):
        self.an_obj = obj

    def __getattr__(self, method_name):
        def method(*args, **kwargs):
            print("Handling unknown method: '{}'".format(method_name))
            if kwargs:
                print("It had the following key word arguments: " + str(kwargs))
            if args:
                print("It had the following positional arguments: " + str(args))
            return getattr(self.an_obj, method_name)(*args, **kwargs)
        return method

当您需要应用代理模式时，这非常有用。

此外，考虑到args 和 kwargs，您可以生成一个完全用户友好的界面，因为使用 MagicClass 的人将其视为真实的对象。