从unittest测试调用时，argparse失败

本文介绍了从unittest测试调用时，argparse失败的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

在文件中(例如parser.py)，我有:

In a file (say parser.py) I have:

import argparse def parse_cmdline(cmdline=None): parser = argparse.ArgumentParser() parser.add_argument('--first-param',help="Does foo.") parser.add_argument('--second-param',help="Does bar.") if cmdline is not None: args = parser.parse_args(cmdline) else: args = parser.parse_args() return vars(args) if __name__=='__main__': print parse_cmdline()

可以肯定的是，当从命令行调用它时，它可以正常工作，并且可以给我很多我所期望的东西:

Sure enough, when called from the command line it works and give me pretty much what I expect:

$ ./parser.py --first-param 123 --second-param 456 {'first_param': '123', 'second_param': '456'}

但是随后我想unittest它，因此我写了一个test_parser.py文件:

But then I want to unittest it, thus I write a test_parser.py file:

import unittest from parser import parse_cmdline class TestParser(unittest.TestCase): def test_parse_cmdline(self): parsed = parse_cmdline("--first-param 123 --second-param 456") self.assertEqual(parsed['first_param'],'123') self.assertEqual(parsed['second_param'],'456') if __name__ == '__main__': unittest.main()

然后我得到以下错误:

usage: test_parser.py [-h] [--first-param FIRST_PARAM] [--second-param SECOND_PARAM] test_parser.py: error: unrecognized arguments: - - f i r s t - p a r a m 1 2 3 - - s e c o n d - p a r a m 4 5 6 E ====================================================================== ERROR: test_parse_cmdline (__main__.TestParser) ---------------------------------------------------------------------- Traceback (most recent call last): File "./test_parser.py", line 8, in test_parse_cmdline parsed = parse_cmdline("--first-param 123 --second-param 456") File "/home/renan/test_argparse/parser.py", line 12, in parse_cmdline args = parser.parse_args(cmdline) File "/usr/lib/python2.7/argparse.py", line 1691, in parse_args self.error(msg % ' '.join(argv)) File "/usr/lib/python2.7/argparse.py", line 2361, in error self.exit(2, _('%s: error: %s\n') % (self.prog, message)) File "/usr/lib/python2.7/argparse.py", line 2349, in exit _sys.exit(status) SystemExit: 2 ---------------------------------------------------------------------- Ran 1 test in 0.004s FAILED (errors=1)

可以看出，我指定的命令行(--first-param 123 --second-param 456)变成了 - - f i r s t - p a r a m 1 2 3 - - s e c o n d - p a r a m 4 5 6(每个字符用空格分隔).

As can be seen, the command line I specified (--first-param 123 --second-param 456) became - - f i r s t - p a r a m 1 2 3 - - s e c o n d - p a r a m 4 5 6 (each character is separated by a space).

我不明白为什么:我做错了什么?

I don't understand why: what am I doing wrong?

推荐答案

argparse希望有一个参数向量"(即单独的参数列表)，而不是命令行"字符串.

argparse wants an "argument vector"—that is, a list of separate arguments—not a "command line" string.

仅调用split不会解决问题.例如，从命令行输入以下命令行:

And just calling split won't solve things. For example, this command line from the shell:

python script.py --first-param '123 456' --second-param 789

…可以正确地给您123 456和789，但这行代码是

… will correctly give you 123 456 and 789, but this line of code:

parse_cmdline("--first-param '123 456' --second-param 789")

不会；它将为您提供'123和789，还有一个额外的456'，它不知道如何处理.

will not; it will give you '123 and 789, with an extra 456' that it doesn't know how to deal with.

事实上，即使这是错误的:

In fact, even this is wrong:

parse_cmdline("--first-param '123' --second-param 789")

...因为您将获得'123'而不是123.

… because you'll get '123' instead of 123.

有两种处理方法.

首先，如果您知道要传递的内容，则可以仅将其作为列表而不是字符串进行传递，并且无需担心引用和拆分细节:

First, if you know what you're trying to pass, you can just pass it as a list instead of a string in the first place, and you don't need to worry about fiddly quoting and splitting details:

parse_cmdline(["--first-param", "123 456", "--second-param", "789"])

或者，如果您不完全知道要传递的内容，则只知道它在外壳上的外观，则可以使用 shlex :

Alternatively, if you don't know exactly what you're trying to pass, you just know what it looks like on the shell, you can use shlex:

if cmdline is not None: args = parser.parse_args(shlex.split(cmdline))

…，现在Python将以与标准Unix shell相同的方式拆分命令行，将123 456作为单个参数.

… and now Python will split your command line the same way as a standard Unix shell, getting the 123 456 as a single parameter.