文档测试
看到Python的官方文档，很多都有示例代码，比如re模块就带了很多示例代码：
>>> import re
>>> m = re.search('(?<=abc)def', 'abcdef')
>>> m.group(0)
'def'
可以把示例代码在Python的交互式环境下输入执行，结果与文档的示例代码显示的一致。
当我们编写注释，写上下面的注释更友好：
def abs(n):
'''
Function to get absolute value of number.
Example:
>>> abs(1)
1
>>> abs(-1)
1
>>>abs(0)
0
'''
return n if n >= 0 else (-n)
好处：
- 告诉函数的调用者该函数期望输入和输出
- 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
- doctest 严格按照Python交互式命令行的输入和输出判断测试结果是否正确，只有测试异常的时候，可以用...表示一大推输出
使用doctest来测试编写的Dict类：
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()
运行后什么也没输出，这说明编写的doctest运行都是正确的， 如果程序有问题，比如我们试着把 __ getattr__ 注释掉，
会有就会有报错：
注释如下：
# def __getattr__(self, key):
# try:
# return self[key]
# except KeyError:
# raise AttributeError(r"'Dict' object has no attribute '%s'" % key)
执行结果，报错内容：
Error
**********************************************************************
File "E:/pyplace/learn_python3/learn/two/测试/文档测试/mydict2.py", line 7, in Dict
Failed example:
d1.x
Exception raised:
Traceback (most recent call last):
File "D:\JetBrains\PyCharm 2018.1.1\helpers\pycharm\docrunner.py", line 140, in __run
compileflags, 1), test.globs)
File "<doctest Dict[2]>", line 1, in <module>
d1.x
AttributeError: 'Dict' object has no attribute 'x'
Error
**********************************************************************
File "E:/pyplace/learn_python3/learn/two/测试/文档测试/mydict2.py", line 13, in Dict
Failed example:
d2.c
Exception raised:
Traceback (most recent call last):
File "D:\JetBrains\PyCharm 2018.1.1\helpers\pycharm\docrunner.py", line 140, in __run
compileflags, 1), test.globs)
File "<doctest Dict[6]>", line 1, in <module>
d2.c
AttributeError: 'Dict' object has no attribute 'c'
Process finished with exit code 0
总结：
- Python 官方文档的示例代码，可以在Python 交互式环境下执行。
- 写注释会显得更加有好
