Python -- 文档测试

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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。

例子：

# mydict2.py
class Dict(dict):
    '''
    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__':
    import doctest
    doctest.testmod()

如果程序没有错误，则没有输出

如果程序有问题，比如把__getattr__()方法注释掉，再运行就会报错：

>>> 
**********************************************************************
File "C:UsersSQDDesktopGitPythondoctestmydict2.py", line 12, in __main__.Dict
Failed example:
    d1['y']
Exception raised:
    Traceback (most recent call last):
      File "C:Python34libdoctest.py", line 1324, in __run
        compileflags, 1), test.globs)
      File "<doctest __main__.Dict[4]>", line 1, in <module>
        d1['y']
    KeyError: 'y'
**********************************************************************
1 items had failures:
   1 of   9 in __main__.Dict
***Test Failed*** 1 failures.

注意到最后3行代码。当模块正常导入时，doctest不会被执行。只有在命令行直接运行时，才执行doctest。所以，不必担心doctest会在非测试环境下执行。