作为一个有用的副作用，它还能为我们带来代码的单元测试和说明文档。
As a useful side-effect, it also provides us with unit testing and documentation of our code.
此代码还举例说明了指定回调的参数的一种方法：作为一个匿名列表，具有到作为第一个参数的回调的引用，随后是所需的参数。
This code also demonstrates one way to specify arguments to a callback: as an anonymous list, with a reference to the callback invoked as the first element, followed by the required parameters.
这对于跟非开发人员解释软件的运行来说非常之有用，同时也可作为针对后来者或者代码修改人员的一份很有价值的文档说明。
This can be valuable in explaining the software to non-developers or it could be useful documentation for when a software design needs to be learned by others and modified later.
清单3中的程序说明了如何在Python中完成这项工作：这段代码接受一个tar文件的名称作为命令行参数，然后向用户提供几种选择。
The program in Listing 3 shows how to do that in Python: the code takes a tar filename as a command-line argument and then prompts the user with several options.
清单3中的程序说明了如何在Python中完成这项工作：这段代码接受一个tar文件的名称作为命令行参数，然后向用户提供几种选择。
The program in Listing 3 shows how to do that in Python: the code takes a tar filename as a command-line argument and then prompts the user with several options.
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