开发程序时不使用重装的最佳方式

Question

我从其他讨论中看到，重装被认为是不必要的操作，也是开发程序的坏方法。人们说使用doctest和unittest。我肯定错过了什么。为了开发一个程序，我把它写在一个模块中，将模块加载到Eclipse控制台中，通过运行少量代码示例在控制台中进行试验，然后在模块中发现错误或决定更改某些内容。最快的做法是保存模块，重新加载并在控制台中继续工作。
有没有更好的方法？

Answer 1

这里有一个如何你可以在比较通过在控制台输入代码，用递归阶乘函数被用作一个实例使用doctest和测试驱动的开发与测试一个人为的例子：

控制台：

第一次尝试：

def factorial(x) 
    pass 

控制台：

>>> factorial(7) 
SyntaxError: invalid syntax 

第二次尝试：

def factorial(x): 
    return x*x-1 

控制台：

>>> factorial(7) 
42 

第三次尝试：

​​

控制台：

>>> factorial(7) 
RuntimeError: maximum recursion depth reached  # StackOverflow! (basically) 

第四次尝试：

def factorial(x): 
    if x == 0: 
     return 1 
    else: 
     return x * factorial(x-1) 

控制台：

>>> factorial(5) 
120 

最终，我们得到正确的答案，但在每一个阶段，我们必须回到控制台和写同样的事情。对于像这样的短程序来说，这是可以的，但对于具有许多功能的程序，以及更复杂的交互和可能被测试的程序来说，这需要很长时间。编程是关于重复性任务的自动化，而测试是一个重复的任务，所以自动化它是有意义的。在Python中，为您提供的工具就是为您提供的。

看哪 - 该文档测试模块（例如，从文档拍摄）

第一次尝试：

def factorial(n): 
    """Return the factorial of n, an exact integer >= 0. 

    >>> [factorial(n) for n in range(6)] 
    [1, 1, 2, 6, 24, 120] 
    >>> factorial(30) 
    265252859812191058636308480000000 
    >>> factorial(-1) 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be >= 0 

    Factorials of floats are OK, but the float must be an exact integer: 
    >>> factorial(30.1) 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be exact integer 
    >>> factorial(30.0) 
    265252859812191058636308480000000 

    It must also not be ridiculously large: 
    >>> factorial(1e100) 
    Traceback (most recent call last): 
     ... 
    OverflowError: n too large 
    """ 

if __name__ == "__main__": 
    import doctest 
    doctest.testmod(verbose=True) 

首先测试（只运行程序）：

Trying: 
    [factorial(n) for n in range(6)] 
Expecting: 
    [1, 1, 2, 6, 24, 120] 
ok 
Trying: 
    factorial(30) 
Expecting: 
    265252859812191058636308480000000 
ok 
Trying: 
    factorial(-1) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be >= 0 
ok 
Trying: 
    factorial(30.1) 
Expecting: 
    Traceqwrqaeqrback (most recent call last): 
     ... 
    ValueError: n must be exact integer 
********************************************************************** 
File "C:/Python33/doctestex.py", line 14, in __main__.factorial 
Failed example: 
    factorial(30.1) 
Exception raised: 
    Traceback (most recent call last): 
     File "C:\Python33\lib\doctest.py", line 1287, in __run 
     compileflags, 1), test.globs) 
     File "<doctest __main__.factorial[3]>", line 1, in <module> 
     factorial(30.1) 
     File "C:/Python33/doctestex.py", line 32, in factorial 
     raise ValueError("n must be exact integer") 
    ValueError: n must be exact integer 
Trying: 
    factorial(30.0) 
Expecting: 
    265252859812191058636308480000000 
ok 
Trying: 
    factorial(1e100) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    OverflowError: n too large 
ok 
1 items had no tests: 
    __main__ 
********************************************************************** 
1 items had failures: 
    1 of 6 in __main__.factorial 
6 tests in 2 items. 
5 passed and 1 failed. 
***Test Failed*** 1 failures. 
>>> ================================ RESTART ================================ 
>>> 
Trying: 
    [factorial(n) for n in range(6)] 
Expecting: 
    [1, 1, 2, 6, 24, 120] 
********************************************************************** 
File "C:/Python33/doctestex.py", line 4, in __main__.factorial 
Failed example: 
    [factorial(n) for n in range(6)] 
Expected: 
    [1, 1, 2, 6, 24, 120] 
Got: 
    [None, None, None, None, None, None] 
Trying: 
    factorial(30) 
Expecting: 
    265252859812191058636308480000000 
********************************************************************** 
File "C:/Python33/doctestex.py", line 6, in __main__.factorial 
Failed example: 
    factorial(30) 
Expected: 
    265252859812191058636308480000000 
Got nothing 
Trying: 
    factorial(-1) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be >= 0 
********************************************************************** 
File "C:/Python33/doctestex.py", line 8, in __main__.factorial 
Failed example: 
    factorial(-1) 
Expected: 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be >= 0 
Got nothing 
Trying: 
    factorial(30.1) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be exact integer 
********************************************************************** 
File "C:/Python33/doctestex.py", line 14, in __main__.factorial 
Failed example: 
    factorial(30.1) 
Expected: 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be exact integer 
Got nothing 
Trying: 
    factorial(30.0) 
Expecting: 
    265252859812191058636308480000000 
********************************************************************** 
File "C:/Python33/doctestex.py", line 18, in __main__.factorial 
Failed example: 
    factorial(30.0) 
Expected: 
    265252859812191058636308480000000 
Got nothing 
Trying: 
    factorial(1e100) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    OverflowError: n too large 
********************************************************************** 
File "C:/Python33/doctestex.py", line 22, in __main__.factorial 
Failed example: 
    factorial(1e100) 
Expected: 
    Traceback (most recent call last): 
     ... 
    OverflowError: n too large 
Got nothing 
1 items had no tests: 
    __main__ 
********************************************************************** 
1 items had failures: 
    6 of 6 in __main__.factorial 
6 tests in 2 items. 
0 passed and 6 failed. 
***Test Failed*** 6 failures. 

那么当我们完成程序（以及之间的所有阶段），我们只需按一个按钮，即可完成我们所有的测试。如果您正在与一个团队合作开发一个更大的项目，那么您可以将测试数据写入文件并使用失败来查看需要关注的位置。

Trying: 
    [factorial(n) for n in range(6)] 
Expecting: 
    [1, 1, 2, 6, 24, 120] 
ok 
Trying: 
    factorial(30) 
Expecting: 
    265252859812191058636308480000000 
ok 
Trying: 
    factorial(-1) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be >= 0 
ok 
Trying: 
    factorial(30.1) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be exact integer 
ok 
Trying: 
    factorial(30.0) 
Expecting: 
    265252859812191058636308480000000 
ok 
Trying: 
    factorial(1e100) 
Expecting: 
    Traceback (most recent call last): 
     ... 
    OverflowError: n too large 
ok 
1 items had no tests: 
    __main__ 
1 items passed all tests: 
    6 tests in __main__.factorial 
6 tests in 2 items. 
6 passed and 0 failed. 
Test passed. 

和（前提是您添加的所有测试用例文档字符串），现在你可以运送或整合或任何程序，它少得多的错误比，如果你只是测试你觉得要紧的事情就真是每次你改变了一些东西，而不是你在开发过程开始时可能会遇到的事情。

更不用提你现在有你的文档的基础！在控制台中运行该程序，然后进入help(factorial)现在给你这样的：

Help on function factorial in module __main__: 

factorial(n) 
    Return the factorial of n, an exact integer >= 0. 

    >>> [factorial(n) for n in range(6)] 
    [1, 1, 2, 6, 24, 120] 
    >>> factorial(30) 
    265252859812191058636308480000000 
    >>> factorial(-1) 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be >= 0 

    Factorials of floats are OK, but the float must be an exact integer: 
    >>> factorial(30.1) 
    Traceback (most recent call last): 
     ... 
    ValueError: n must be exact integer 
    >>> factorial(30.0) 
    265252859812191058636308480000000 

    It must also not be ridiculously large: 
    >>> factorial(1e100) 
    Traceback (most recent call last): 
     ... 
    OverflowError: n too large 

然后，您可以使用一些工具（pydoc是一个标准库）打开文档字符串成格式化的HTML帮助文档。

当然，这只是您可以在Python中使用的许多测试工具之一。其他功能包括功能更强大的unittest模块，以及将assert语句添加到代码中的功能较弱的技术。

Answer 2

基本上不是在控制台中尝试一下，而是通过编写测试来尝试一些事情。这几乎与键入的量相同，但是可重复（您可以检查更改后是否仍然有效），并且它可以作为文档的基本形式。