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:\Users\SQD\Desktop\Git\Python\doctest\mydict2.py", line 12, in __main__.Dict
Failed example:
d1['y']
Exception raised:
Traceback (most recent call last):
File "C:\Python34\lib\doctest.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。