自定义 argparse 帮助信息

Question

我编写了以下示例代码来演示我的问题。

 import argparse

parser = argparse.ArgumentParser()
parser.add_argument('-v', '--version', action='version',
                    version='%(prog)s 1.0')
parser.parse_args()

这会产生以下帮助消息。

 $ python foo.py --help
usage: foo.py [-h] [-v]

optional arguments:
  -h, --help     show this help message and exit
  -v, --version  show program's version number and exit

我想自定义此帮助输出，使其将所有短语和句子大写，并在句子后加上句号。换句话说，我希望这样生成帮助消息。

 $ python foo.py --help
Usage: foo.py [-h] [-v]

Optional arguments:
  -h, --help     Show this help message and exit.
  -v, --version  Show program's version number and exit.

这是我可以使用 argparse API 控制的东西吗？如果是这样，如何？你能提供一个小例子来说明如何做到这一点吗？

原文由 Lone Learner 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

首先：大写这些短语与惯例背道而驰，而且 argparse 并没有真正帮助您轻松更改这些字符串的工具。这里有三种不同类别的字符串：来自帮助格式化程序的样板文本、部分标题和每个特定选项的帮助文本。所有这些字符串都是可本地化的；您 可以 通过 gettext() 模块支持 为所有这些字符串提供“大写”翻译。也就是说，如果您有足够的决心并 稍微阅读源代码，您可以深入并替换所有这些字符串。

version 操作包含默认的 help 文本，但您可以通过设置 help 参数来提供您自己的文本。这同样适用于 help 动作；如果您将 add_help 参数 设置为 False 您可以手动添加该操作：

 parser = argparse.ArgumentParser(add_help=False)

parser.add_argument('-v', '--version', action='version',
                    version='%(prog)s 1.0', help="Show program's version number and exit.")
parser.add_argument('-h', '--help', action='help', default=argparse.SUPPRESS,
                    help='Show this help message and exit.')

接下来， optional arguments 消息是 _组标题_；每个解析器都有两个默认组，一个用于位置参数，另一个用于可选。您可以通过属性 _positionals 和 _optionals 来访问它们，它们都有一个 title 属性：

 parser._positionals.title = 'Positional arguments'
parser._optionals.title = 'Optional arguments'

_请注意_，通过访问以下划线开头的名称，您正在冒险进入模块的未记录的私有 API，您的代码可能会在未来的更新中中断。

最后，要更改 usage 字符串，您必须继承帮助格式化程序；将子类作为 formatter_class 参数 传递：

 class CapitalisedHelpFormatter(argparse.HelpFormatter):
    def add_usage(self, usage, actions, groups, prefix=None):
        if prefix is None:
            prefix = 'Usage: '
        return super(CapitalisedHelpFormatter, self).add_usage(
            usage, actions, groups, prefix)

parser = argparse.ArgumentParser(formatter_class=CapitalisedHelpFormatter)

演示，将这些放在一起：

 >>> import argparse
>>> class CapitalisedHelpFormatter(argparse.HelpFormatter):
...     def add_usage(self, usage, actions, groups, prefix=None):
...         if prefix is None:
...             prefix = 'Usage: '
...         return super(CapitalisedHelpFormatter, self).add_usage(
...             usage, actions, groups, prefix)
...
>>> parser = argparse.ArgumentParser(add_help=False, formatter_class=CapitalisedHelpFormatter)
>>> parser._positionals.title = 'Positional arguments'
>>> parser._optionals.title = 'Optional arguments'
>>> parser.add_argument('-v', '--version', action='version',
...                     version='%(prog)s 1.0', help="Show program's version number and exit.")
_VersionAction(option_strings=['-v', '--version'], dest='version', nargs=0, const=None, default='==SUPPRESS==', type=None, choices=None, help="Show program's version number and exit.", metavar=None)
>>> parser.add_argument('-h', '--help', action='help', default=argparse.SUPPRESS,
...                     help='Show this help message and exit.')
_HelpAction(option_strings=['-h', '--help'], dest='help', nargs=0, const=None, default='==SUPPRESS==', type=None, choices=None, help='Show this help message and exit.', metavar=None)
>>> print(parser.format_help())
Usage: [-v] [-h]

Optional arguments:
  -v, --version  Show program's version number and exit.
  -h, --help     Show this help message and exit.

原文由 Martijn Pieters 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

不依赖于内部 API（如有更改，恕不另行通知），这里有一个仅使用公共 API 的替代方案。它可以说更复杂，但反过来可以让您最大程度地控制打印的内容：

 class ArgumentParser(argparse.ArgumentParser):

    def __init__(self, *args, **kwargs):
        super(ArgumentParser, self).__init__(*args, **kwargs)
        self.program = { key: kwargs[key] for key in kwargs }
        self.options = []

    def add_argument(self, *args, **kwargs):
        super(ArgumentParser, self).add_argument(*args, **kwargs)
        option = {}
        option["flags"] = [ item for item in args ]
        for key in kwargs:
            option[key] = kwargs[key]
        self.options.append(option)

    def print_help(self):
        # Use data stored in self.program/self.options to produce
        # custom help text

这个怎么运作：

• 进入 argparse.ArgumentParser 捕获和存储程序信息（例如描述、使用）到 self.program
• 利用 argparse.ArgumentParser.add_argument() 捕获并存储添加的参数（例如标志、帮助、默认值）到 self.options
• 重新定义 argparse.ArgumentParser.print_help() 并使用之前存储的程序信息/参数来生成帮助文本

---

这是一个涵盖一些常见用例的完整示例。请注意，这绝不是完整的（例如，不支持位置参数或具有多个参数的选项），但它应该提供一个可能的好印象：

 #!/usr/bin/env python3
# -*- coding: utf-8 -*-

import os
import sys
import argparse
import textwrap

class ArgumentParser(argparse.ArgumentParser):

    def __init__(self, *args, **kwargs):
        super(ArgumentParser, self).__init__(*args, **kwargs)
        self.program = { key: kwargs[key] for key in kwargs }
        self.options = []

    def add_argument(self, *args, **kwargs):
        super(ArgumentParser, self).add_argument(*args, **kwargs)
        option = {}
        option["flags"] = [ item for item in args ]
        for key in kwargs:
            option[key] = kwargs[key]
        self.options.append(option)

    def print_help(self):
        wrapper = textwrap.TextWrapper(width=80)

        # Print usage
        if "usage" in self.program:
            print("Usage: %s" % self.program["usage"])
        else:
            usage = []
            for option in self.options:
                usage += [ "[%s %s]" % (item, option["metavar"]) if "metavar" in option else "[%s %s]" % (item, option["dest"].upper()) if "dest" in option else "[%s]" % item for item in option["flags"] ]
            wrapper.initial_indent = "Usage: %s " % os.path.basename(sys.argv[0])
            wrapper.subsequent_indent = len(wrapper.initial_indent) * " "
            output = str.join(" ", usage)
            output = wrapper.fill(output)
            print(output)
        print()

        # Print description
        if "description" in self.program:
            print(self.program["description"])
            print()

        # Print options
        print("Options:")
        maxlen = 0
        for option in self.options:
            option["flags2"] = str.join(", ", [ "%s %s" % (item, option["metavar"]) if "metavar" in option else "%s %s" % (item, option["dest"].upper()) if "dest" in option else item for item in option["flags"] ])
            if len(option["flags2"]) > maxlen:
                maxlen = len(option["flags2"])
        for option in self.options:
            template = "  %-" + str(maxlen) + "s  "
            wrapper.initial_indent = template % option["flags2"]
            wrapper.subsequent_indent = len(wrapper.initial_indent) * " "
            if "help" in option and "default" in option:
                output = option["help"]
                output += " (default: '%s')" % option["default"] if isinstance(option["default"], str) else " (default: %s)" % str(option["default"])
                output = wrapper.fill(output)
            elif "help" in option:
                output = option["help"]
                output = wrapper.fill(output)
            elif "default" in option:
                output = "Default: '%s'" % option["default"] if isinstance(option["default"], str) else "Default: %s" % str(option["default"])
                output = wrapper.fill(output)
            else:
                output = wrapper.initial_indent
            print(output)

# Main
if (__name__ == "__main__"):
    #parser = argparse.ArgumentParser(description="Download program based on some library.", argument_default=argparse.SUPPRESS, allow_abbrev=False, add_help=False)
    #parser = argparse.ArgumentParser(usage="%s [OPTION]..." % os.path.basename(sys.argv[0]), description="Download program based on some library.", argument_default=argparse.SUPPRESS, allow_abbrev=False, add_help=False)
    #parser = ArgumentParser(usage="%s [OPTION]..." % os.path.basename(sys.argv[0]), description="Download program based on some library.", argument_default=argparse.SUPPRESS, allow_abbrev=False, add_help=False)
    parser = ArgumentParser(description="Download program based on some library.", argument_default=argparse.SUPPRESS, allow_abbrev=False, add_help=False)

    parser.add_argument("-c", "--config-file", action="store", dest="config_file", metavar="file", type=str, default="config.ini")
    parser.add_argument("-d", "--database-file", action="store", dest="database_file", metavar="file", type=str, help="SQLite3 database file to read/write", default="database.db")
    parser.add_argument("-l", "--log-file", action="store", dest="log_file", metavar="file", type=str, help="File to write log to", default="debug.log")
    parser.add_argument("-f", "--data-file", action="store", dest="data_file", metavar="file", type=str, help="Data file to read", default="data.bin")
    parser.add_argument("-t", "--threads", action="store", dest="threads", type=int, help="Number of threads to spawn", default=3)
    parser.add_argument("-p", "--port", action="store", dest="port", type=int, help="TCP port to listen on for access to the web interface", default="12345")
    parser.add_argument("--max-downloads", action="store", dest="max_downloads", metavar="value", type=int, help="Maximum number of concurrent downloads", default=5)
    parser.add_argument("--download-timeout", action="store", dest="download_timeout", metavar="value", type=int, help="Download timeout in seconds", default=120)
    parser.add_argument("--max-requests", action="store", dest="max_requests", metavar="value", type=int, help="Maximum number of concurrent requests", default=10)
    parser.add_argument("--request-timeout", action="store", dest="request_timeout", metavar="value", type=int, help="Request timeout in seconds", default=60)
    parser.add_argument("--main-interval", action="store", dest="main_interval", metavar="value", type=int, help="Main loop interval in seconds", default=60)
    parser.add_argument("--thread-interval", action="store", dest="thread_interval", metavar="value", type=int, help="Thread loop interval in milliseconds", default=500)
    parser.add_argument("--console-output", action="store", dest="console_output", metavar="value", type=str.lower, choices=["stdout", "stderr"], help="Output to use for console", default="stdout")
    parser.add_argument("--console-level", action="store", dest="console_level", metavar="value", type=str.lower, choices=["debug", "info", "warning", "error", "critical"], help="Log level to use for console", default="info")
    parser.add_argument("--logfile-level", action="store", dest="logfile_level", metavar="value", type=str.lower, choices=["debug", "info", "warning", "error", "critical"], help="Log level to use for log file", default="info")
    parser.add_argument("--console-color", action="store", dest="console_color", metavar="value", type=bool, help="Colorized console output", default=True)
    parser.add_argument("--logfile-color", action="store", dest="logfile_color", metavar="value", type=bool, help="Colorized log file output", default=False)
    parser.add_argument("--log-template", action="store", dest="log_template", metavar="value", type=str, help="Template to use for log lines", default="[%(created)d] [%(threadName)s] [%(levelname)s] %(message)s")
    parser.add_argument("-h", "--help", action="help", help="Display this message")

    args = parser.parse_args(["-h"])

产生的输出：

 Usage: argparse_custom_usage.py [-c file] [--config-file file] [-d file]
                                [--database-file file] [-l file] [--log-file
                                file] [-f file] [--data-file file] [-t THREADS]
                                [--threads THREADS] [-p PORT] [--port PORT]
                                [--max-downloads value] [--download-timeout
                                value] [--max-requests value] [--request-timeout
                                value] [--main-interval value] [--thread-
                                interval value] [--console-output value]
                                [--console-level value] [--logfile-level value]
                                [--console-color value] [--logfile-color value]
                                [--log-template value] [-h] [--help]

Download program based on some library.

Options:
  -c file, --config-file file    Default: 'config.ini'
  -d file, --database-file file  SQLite3 database file to read/write (default:
                                 'database.db')
  -l file, --log-file file       File to write log to (default: 'debug.log')
  -f file, --data-file file      Data file to read (default: 'data.bin')
  -t THREADS, --threads THREADS  Number of threads to spawn (default: 3)
  -p PORT, --port PORT           TCP port to listen on for access to the web
                                 interface (default: '12345')
  --max-downloads value          Maximum number of concurrent downloads
                                 (default: 5)
  --download-timeout value       Download timeout in seconds (default: 120)
  --max-requests value           Maximum number of concurrent requests (default:
                                 10)
  --request-timeout value        Request timeout in seconds (default: 60)
  --main-interval value          Main loop interval in seconds (default: 60)
  --thread-interval value        Thread loop interval in milliseconds (default:
                                 500)
  --console-output value         Output to use for console (default: 'stdout')
  --console-level value          Log level to use for console (default: 'info')
  --logfile-level value          Log level to use for log file (default: 'info')
  --console-color value          Colorized console output (default: True)
  --logfile-color value          Colorized log file output (default: False)
  --log-template value           Template to use for log lines (default:
                                 '[%(created)d] [%(threadName)s] [%(levelname)s]
                                 %(message)s')
  -h, --help                     Display this message

---

编辑：

如果此后显着扩展了示例，并将继续在 GitHub 上 这样做。

原文由 Fonic 发布，翻译遵循 CC BY-SA 4.0 许可协议