在不使用重新加载的情况下开发程序的最佳方法

时间：2013-10-30 11:04:35

标签： python

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，也是开发程序的一种糟糕方式。人们说使用doctest和unittest。我肯定错过了什么。要开发一个程序，我将它写在一个模块中，将模块加载到eclipse控制台，通过运行少量代码示例在控制台中进行实验，然后我发现模块中的错误或决定更改某些内容。当然，最快的方法是保存模块，重新加载并继续在控制台中工作 有没有更好的办法？

2 个答案:

答案 0 :(得分：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（您可以检查更改后是否仍然有效）并且它可以作为一种基本的文档形式。

答案 1 :(得分：0)

这是一个人为的例子，说明如何使用doctest和测试驱动开发，通过在控制台输入代码进行测试，并以递归因子函数为例：

控制台：

首次尝试：

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回到控制台并编写相同的内容。这对于像这样的短程序来说是好的，但是对于具有许多功能的程序，以及更复杂的交互和可能性进行测试，这将花费很长时间。编程是关于自动执行重复性任务，而测试是一项重复性任务，因此将其自动化是有意义的。在Python中，为您提供了这样做的工具。

看哪 - doctest模块:(来自文档的例子）

首次尝试：

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.

然后，当我们完成程序（以及之间的所有阶段）时，我们只需按一个按钮即可完成我们的所有测试。如果您正在与一个更大项目的团队合作，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.

并且（如果您将所有测试用例添加到文档字符串中）现在您可以发送或集成任何程序，并且如果您在每次更改时只测试了您认为重要的事情，那么它将会出现更少的错误事情，而不是你认为在开发过程开始时可能会发生的事情。

更不用说您现在拥有文档的基础！在控制台中运行程序，然后输入help(factorial)现在将为您提供：

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，您可以使用许多工具（pydoc是标准库中的一个）将文档字符串转换为格式化的HTML帮助文件。

当然，这只是可以与Python一起使用的众多测试工具之一。其他包括更强大的unittest模块，以及在代码中添加assert语句的功能较弱的技术。

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