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What is the difference between a positional argument and an optional argument (flag) in argparse? How do you specify a default value and a type conversion for an argument? How do you restrict an argument's accepted values using the 'choices' parameter? How do you accept a variable number of arguments for a single flag, like a list of filenames? How do you provide a short and a long form for the same flag, like -v and --verbose? How do you implement subcommands (like 'git commit' or 'git push') using argparse's add_subparsers()? How do you group related arguments visually in the generated --help output using argument groups? How do you implement mutually exclusive arguments, where the user must choose EXACTLY ONE of a set of flags? How do you write a custom 'type=' validation function for argparse that raises a properly-formatted error for invalid input? How would you build a CLI tool where some arguments can also be set via environment variables, falling back to a default if neither is provided?
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How do you implement boolean flags using action='store_true' and action='store_false'?

Intermediate

Answer

'action="store_true"' makes a flag default to False and become True if PRESENT on the command line (no value needed after it); 'action="store_false"' is the inverse, defaulting to True and becoming False if present — both avoid needing the user to type an explicit 'True'/'False' string.
parser.add_argument("--verbose", action="store_true", help="Enable verbose output")
parser.add_argument("--no-color", action="store_false", dest="use_color", help="Disable colored output")
args = parser.parse_args(["--verbose"])
print(args.verbose)    # True
print(args.use_color)  # True (default, since --no-color wasn't passed)
Real-world example Implementing a simple --verbose or --debug toggle flag that doesn't require a value, just its presence or absence.

Common follow-ups: How does the 'dest' parameter let a flag named '--no-color' set an attribute actually named 'use_color'?

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All 15 Command-Line Interfaces (argparse) questions