47-文档测试（1）

文档测试：

Python内置的“文档测试”（doctest）模块可以直接提取注释中的代码并执行测试。

# mydict2.py
class Dict(dict): #下面这些'''xxx'''部分即为自定义的测试语句，写成了注释。
    '''
    Simple dict but also support access as x.y style.

    >>> d1 = Dict()
    >>> d1['x'] = 100
    >>> d1.x
    100
    >>> d1.y = 200
    >>> d1['y']
    200
    >>> d2 = Dict(a=1, b=2, c='3')
    >>> d2.c
    '3'
    >>> d2['empty']
    Traceback (most recent call last):
        ...
    KeyError: 'empty'
    >>> d2.empty
    Traceback (most recent call last):
        ...
    AttributeError: 'Dict' object has no attribute 'empty'
    '''
    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

if __name__=='__main__': #当且仅当运行 {mydict2}时，才发生if后面的语句
    import doctest
    doctest.testmod()
    
#若没有任何输出，说明测试通过,否则就是有错误