python 中__getattr__ 以及 __setattr__

python 中__getattr__ 以及 __setattr__

下面是mydict.py:

#!/usr/bin/env python

class Dict(dict):

    def __init__(self, **kw):
        super(Dict, self).__init__(**kw)

    def __getattr__(self, key):
        try:
            return self[key]
        except KeyError:
            raise AttributeError(r"‘Dict‘ object has no attribute ‘%s‘" % key)

    def __setattr__(self, key, value):
        self[key] = value

d = Dict(a=1, b=2)
print d[‘a‘]
# use __getattr__ function
print d.a
print d.b
# use __setattr__ function
d.b = 3
print d.b
#print d.c

class Test():
    def __getattr__(self, a):
        return a

t = Test()
print t.ni

结果为：

1
1
2
3
ni

运行单元测试：

import unittest

from mydict import Dict

class TestDict(unittest.TestCase):

    def setUp(self):
        print(‘setUp...‘)

    def tearDown(self):
        print(‘tearDown...‘)

    def test_init(self):
        d = Dict(a=1, b=‘test‘)
        self.assertEqual(d.a, 1)
        self.assertEqual(d.b, ‘test‘)
        self.assertTrue(isinstance(d, dict))

    def test_key(self):
        d = Dict()
        d[‘key‘] = ‘value‘
        self.assertEqual(d.key, ‘value‘)

    def test_attr(self):
        d = Dict()
        d.key = ‘value‘
        self.assertTrue(‘key‘ in d)
        self.assertEqual(d[‘key‘], ‘value‘)

    def test_keyerror(self):
        d = Dict()
        with self.assertRaises(KeyError):
            value = d[‘empty‘]

    def test_attrerror(self):
        d = Dict()
        with self.assertRaises(AttributeError):
            value = d.empty

if __name__ == ‘__main__‘:
    unittest.main()

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