python - 如何从 plac(Python 命令行解析器)显示默认用法/帮助

Question

我有一个使用“plac”构建的简单命令行程序，这是一个出色的 Python 命令行解析器，我正在尝试以编程方式打印出特定命令的默认用法(也称为“帮助”输出)。

我在“plac”文档中找不到任何内容。感谢您的帮助。

下面是一个示例程序:

import plac

@plac.annotations(
    bootstrap=plac.Annotation("bootstrap", "option", "b", str),
    repo=plac.Annotation("repo to load", "option", "r", str),
    similar=plac.Annotation("term (word|pos) to find similarities, requires 'term'", "flag", "s"),
    mostsimilar=plac.Annotation("similar words to find, requires 'term'", "flag", "m"),
    similarity=plac.Annotation("similarity between two words, requires 'term' and 'term2", "flag", "S"),
    term=plac.Annotation("term (word|pos)", "option", "t", str),
    term2=plac.Annotation("second term (word|pos)", "option", "T", str)
)
def main(bootstrap, repo, similar, mostsimilar, similarity, term, term2):
    :
    if error:
        # PRINT USAGE HERE
    :
if __name__ == '__main__':
    plac.call(main)

在出现命令行错误时，我想使用代码(上面示例中的“PRINT ERROR HERE”)来显示用法，就像我直接发出帮助命令(“python myCLI.py -h”)时一样:

usage: myCLI.py [-h] [-b BOOTSTRAP] [-r REPO] [-s] [-m] [-S] [-t TERM] [-T TERM2]

optional arguments:
  -h, --help            show this help message and exit
  -b BOOTSTRAP, --bootstrap BOOTSTRAP
                        bootstrap
  -r REPO, --repo REPO  repo to load
  -s, --similar         term (word|pos) to find similarities, requires 'term'
  -m, --mostsimilar     similar words to find, requires 'term'
  -S, --similarity      similarity between two words, requires 'term' and
                        'term2
  -t TERM, --term TERM  term (word|pos)
  -T TERM2, --term2 TERM2
                        second term (word|pos)

Answer 1

在大量阅读和检查源代码，以及从@chepner 和@hpaulj 评论中获得的一些想法后，我找到了一个可行的解决方案。如果使用“-h”(帮助)标志调用 CLI，以下代码片段确实会打印出相同的帮助文本:

parser = plac.parser_from(main)
parser.print_help()

完整的示例代码如下所示:

import plac

@plac.annotations(
    bootstrap=plac.Annotation("bootstrap", "option", "b", str),
    repo=plac.Annotation("repo to load", "option", "r", str),
    similar=plac.Annotation("term (word|pos) to find similarities, requires 'term'", "flag", "s"),
    mostsimilar=plac.Annotation("similar words to find, requires 'term'", "flag", "m"),
    similarity=plac.Annotation("similarity between two words, requires 'term' and 'term2", "flag", "S"),
    term=plac.Annotation("term (word|pos)", "option", "t", str),
    term2=plac.Annotation("second term (word|pos)", "option", "T", str)
)
def main(bootstrap, repo, similar, mostsimilar, similarity, term, term2):
    :
    if error:
        ###### Print help message on error
        parser = plac.parser_from(main)
        parser.print_help()
        ######
    :
if __name__ == '__main__':
    plac.call(main)