Python 文檔測試

文檔測試

看到Python的官方文檔，很多都有示例代碼，比如re模塊就帶了很多示例代碼：

>>> import re
>>> m = re.search('(?<=abc)def', 'abcdef')
>>> m.group(0)
'def'

可以把示例代碼在Python的交互式環境下輸入執行，結果與文檔的示例代碼顯示的一致。

當我們編寫註釋，寫上下面的註釋更友好：

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)

好處：

• 告訴函數的調用者該函數期望輸入和輸出
• Python內置的“文檔測試”（doctest）模塊可以直接提取註釋中的代碼並執行測試
• doctest 嚴格按照Python交互式命令行的輸入和輸出判斷測試結果是否正確，只有測試異常的時候，可以用...表示一大推輸出

使用doctest來測試編寫的Dict類：

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()

運行後什麼也沒輸出，這說明編寫的doctest運行都是正確的， 如果程序有問題，比如我們試着把 __ getattr__ 註釋掉，
會有就會有報錯：

註釋如下：

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

執行結果，報錯內容：

Error
**********************************************************************
File "E:/pyplace/learn_python3/learn/two/測試/文檔測試/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/測試/文檔測試/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

總結：

• Python 官方文檔的示例代碼，可以在Python 交互式環境下執行。
• 寫註釋會顯得更加有好

github地址： https://github.com/shenshizhong/learn_python3