Argparse:在“--help"中包含默认值的方法? [英] Argparse: Way to include default values in '--help'?

问题描述

假设我有以下 argparse 片段:

Suppose I have the following argparse snippet:

diags.cmdln_parser.add_argument( '--scan-time',
                     action  = 'store',
                     nargs   = '?',
                     type    = int,
                     default = 5,
                     help    = "Wait SCAN-TIME seconds between status checks.")

当前，--help 返回:

usage: connection_check.py [-h]
                             [--version] [--scan-time [SCAN_TIME]]

          Test the reliability/uptime of a connection.



optional arguments:
-h, --help            show this help message and exit
--version             show program's version number and exit
--scan-time [SCAN_TIME]
                    Wait SCAN-TIME seconds between status checks.

我更喜欢这样的:

--scan-time [SCAN_TIME]
                    Wait SCAN-TIME seconds between status checks.
                    (Default = 5)

查看帮助格式化程序代码发现选项有限.有没有一种聪明的方法让 argparse 以类似的方式打印 --scan-time 的默认值，或者我应该只是将 help 子类化代码>格式化程序?

Peeking at the help formatter code revealed limited options. Is there a clever way to get argparse to print the default value for --scan-time in a similar fashion, or should I just subclass the help formatter?

推荐答案

使用 argparse.ArgumentDefaultsHelpFormatter 格式化程序:

Use the argparse.ArgumentDefaultsHelpFormatter formatter:

parser = argparse.ArgumentParser(
    # ... other options ...
    formatter_class=argparse.ArgumentDefaultsHelpFormatter)

引用文档:

另一个可用的格式化程序类 ArgumentDefaultsHelpFormatter 将添加有关每个参数的默认值的信息.

The other formatter class available, ArgumentDefaultsHelpFormatter, will add information about the default value of each of the arguments.

请注意，这只适用于定义了帮助文本的参数；如果参数没有 help 值，则没有帮助消息来添加有关默认值 to 的信息.

Note that this only applies to arguments that have help text defined; with no help value for an argument, there is no help message to add information about the default value to.

扫描时间选项的确切输出将变为:

The exact output for your scan-time option then becomes:

  --scan-time [SCAN_TIME]
                        Wait SCAN-TIME seconds between status checks.
                        (default: 5)

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