Question

我想创建一个类，在调用任何可能存在或不存在的方法时都不会Attribute Error：

我的班级：

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

预期输出：

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

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

现在，unknown_method和unknown_method2实际上并不存在于类中，但我们如何在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()

打印

'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，这是代码：

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Proxy pattern时，这非常有用。

而且，同时考虑了 args和kwargs ，允许您生成完全用户友好的界面，因为使用MagicClass的界面将其视为真实对象。

Answer 3

覆盖__getattr__;见http://docs.python.org/reference/datamodel.html

Python：如何拦截一个不存在的方法调用？

3 个答案: