8.15<python cookbook>---属性的代理访问

``` python

#!/usr/bin/env python

# -*- coding: utf-8 -*-

# Pw @ 2017-05-15 10:04:20

class Proxy:

    def __init__(self, obj):

        self._obj = obj

    def __getattr__(self, name):

        print('getattr:', name)

        return getattr(self._obj, name)

    def __setattr__(self, name, value):

        if name.startswith('_'):

            super().__setattr__(name, value)

        else:

            print('setattr:', name, value)

            setattr(self._obj, name, value)

    def __delattr__(self, name):

        if name.startswith('_'):

            super().__delattr__(name)

        else:

            print('delattr:', name)

            delattr(self._obj, name)

class Spam:

    def __init__(self, x):

        self.x = x

    def bar(self, y):

        print('Spam.bar', self.x, y)

s = Spam(2)

p = Proxy(s)

print(p.x)

print(p.bar(3))

p.x = 37

print(p.x)

```

作用: 通过自定义属性访问方法，你可以用不同方式自定义代理类行为 (比如加入日志功

能、只读访问等)。

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