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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"argparse metavar parentheses dropped on usage line","articleBody":"Parentheses in argparse `metavar`s are dropped on the `usage` line but appear as expected in the argument list. In particular, the very first and very last parentheses disappear. It looks from other issues (e.g. #56083) that braces, brackets and parentheses in `metavar`s are problematic, so this may be part of a wider and more difficult set of puzzlers to fix.\r\n\r\nIllustrative code:\r\n\r\n```\r\n#!/usr/bin/python3\r\n\"\"\"Demonstrate parenthesis drops in argparse metavar.\"\"\"\r\nimport argparse\r\n\r\n# The very first and last parentheses disappear in the usage line, but are\r\n# present in the argument list.\r\nparser = argparse.ArgumentParser(\r\n    description='Demonstrate parenthesis drops in argument meta-descriptions')\r\nparser.add_argument(\r\n    'positional',\r\n    help='positional argument',\r\n    metavar='(example) positional')\r\nparser.add_argument(\r\n    '-p',\r\n    '--optional',\r\n    help='optional argument',\r\n    type=int,\r\n    choices=[1, 2],\r\n    metavar='{1 (option A), 2 (option B)}',\r\n    default=1)\r\narguments = parser.parse_args()\r\n\r\nprint(arguments)\r\n```\r\n\r\nWhen this is run with `-h`, the help text is rendered as shown below. Note the parentheses are missing before `option A` and after `example`:\r\n\r\n```\r\nusage: parens.py [-h] [-p {1 option A), 2 (option B)}] (example positional\r\n\r\nDemonstrate parenthesis drops in argument meta-descriptions\r\n\r\npositional arguments:\r\n  (example) positional  positional argument\r\n\r\noptional arguments:\r\n  -h, --help            show this help message and exit\r\n  -p {1 (option A), 2 (option B)}, --optional {1 (option A), 2 (option B)}\r\n                        optional argument\r\n```\r\nI've tried this on Python 3.8.10 and Python 3.10.6.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-102318\n* gh-102438\n* gh-102439\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/tonyle72","@type":"Person","name":"tonyle72"},"datePublished":"2023-02-17T08:06:04.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/101979/cpython/issues/101979"}