不使用重载开发程序的最佳方法

Question

我从其他讨论中看到，重新加载被认为是一种不必要的操作，是制定方案的一种糟糕方式。人们说使用doctest和unittest。我一定错过了什么。为了开发一个程序，我将它写在一个模块中，将模块加载到一个eclipse控制台中，在控制台中运行一些代码样本进行实验，然后我发现模块中的一个错误，或者决定更改一些东西。当然，最快的方法是保存模块，重新加载，然后在控制台中继续工作。
有更好的办法吗？你知道吗

Answer 1

基本上不是在控制台中尝试，而是通过编写测试来尝试。它的输入量几乎相同，但可重复（您可以检查在进行更改后是否仍能正常工作），并且它是文档的基本形式。你知道吗

Answer 2

下面是一个精心设计的示例，说明如何使用doctest和测试驱动开发，与通过在控制台输入代码进行测试进行比较，并以递归阶乘函数为例：

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：

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

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

最后，我们得到了正确的答案，但在每个阶段，我们都必须返回到控制台并编写相同的内容。对于这样一个简短的程序来说，这是可以的，但是对于一个具有许多功能、更复杂的交互和测试可能性的程序来说，这将需要很长的时间。编程是关于自动化重复的任务，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，为您提供了实现这一点的工具。你知道吗

请看-doctest模块：（示例取自docs）

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)

第一次测试（只需运行程序）：

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.

然后当我们完成程序时（以及在这两个阶段之间的所有阶段），我们只需按下一个按钮，就可以完成所有的测试。例如，如果您与一个团队一起处理一个更大的项目，您可以将测试数据写入文件，并使用失败来查看您需要关注的地方。你知道吗

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.

而且（假设您将所有测试用例添加到docstring中）现在您可以发布或集成程序或其他任何程序，并且它的bug比您在每次更改时只测试您认为重要的东西，而不是在开发过程开始时您认为可能重要的东西要少得多。你知道吗

更不用说你现在有了你的文件基础！在控制台中运行程序，然后输入help(factorial)，现在可以得到：

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

然后可以使用许多工具（pydoc是标准库中的一个工具）将docstring转换为格式化的HTML帮助文件。你知道吗

当然，这只是可以与Python一起使用的许多测试工具之一。其他的包括功能更强大的unittest模块，以及将assert语句添加到代码中的功能较弱的技术。你知道吗