83. Using argparse for CLI Parsing

The argparse module in Python is used to handle command-line arguments, providing a simple way to create user-friendly CLI tools. It allows you to specify the arguments your program expects, automatically generates help and usage messages, and handles input validation.

Here are 10 Python code snippets demonstrating different uses of argparse for building command-line interfaces:

1. Basic Argument Parsing

import argparse

def main():
    parser = argparse.ArgumentParser(description="A simple command-line tool")
    parser.add_argument("name", help="Your name")
    args = parser.parse_args()
    print(f"Hello, {args.name}!")

if __name__ == "__main__":
    main()

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2. Optional Arguments with Default Values

import argparse

def main():
    parser = argparse.ArgumentParser(description="Greet a user with an optional age argument")
    parser.add_argument("name", help="Your name")
    parser.add_argument("-a", "--age", type=int, default=30, help="Your age (default is 30)")
    args = parser.parse_args()
    print(f"Hello, {args.name}, you are {args.age} years old!")

if __name__ == "__main__":
    main()

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3. Boolean Flag Argument

import argparse

def main():
    parser = argparse.ArgumentParser(description="A tool with a boolean flag")
    parser.add_argument("--verbose", action="store_true", help="Enable verbose output")
    args = parser.parse_args()
    if args.verbose:
        print("Verbose mode is on")
    else:
        print("Verbose mode is off")

if __name__ == "__main__":
    main()

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4. Multiple Positional Arguments

import argparse

def main():
    parser = argparse.ArgumentParser(description="Summing up numbers")
    parser.add_argument("numbers", type=int, nargs="+", help="Numbers to sum")
    args = parser.parse_args()
    print(f"The sum is: {sum(args.numbers)}")

if __name__ == "__main__":
    main()

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5. Argument Type Conversion

import argparse

def even_or_odd(value):
    ivalue = int(value)
    if ivalue % 2 != 0:
        raise argparse.ArgumentTypeError(f"{value} is not an even number")
    return ivalue

def main():
    parser = argparse.ArgumentParser(description="Check if a number is even")
    parser.add_argument("number", type=even_or_odd, help="An even number")
    args = parser.parse_args()
    print(f"You entered the even number: {args.number}")

if __name__ == "__main__":
    main()

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6. Argument Choices for Limited Values

import argparse

def main():
    parser = argparse.ArgumentParser(description="Choose a color")
    parser.add_argument("color", choices=["red", "green", "blue"], help="Pick a color")
    args = parser.parse_args()
    print(f"You selected the color: {args.color}")

if __name__ == "__main__":
    main()

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7. Mutually Exclusive Arguments

import argparse

def main():
    parser = argparse.ArgumentParser(description="Choose either an option A or B, but not both")
    group = parser.add_mutually_exclusive_group()
    group.add_argument("--option-a", action="store_true", help="Option A")
    group.add_argument("--option-b", action="store_true", help="Option B")
    args = parser.parse_args()

    if args.option_a:
        print("Option A selected")
    elif args.option_b:
        print("Option B selected")
    else:
        print("No option selected")

if __name__ == "__main__":
    main()

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8. Help and Usage Information

import argparse

def main():
    parser = argparse.ArgumentParser(description="A command-line tool with help information")
    parser.add_argument("name", help="Your name")
    parser.add_argument("-a", "--age", type=int, help="Your age")
    args = parser.parse_args()
    print(f"Hello, {args.name}!")
    if args.age:
        print(f"You are {args.age} years old.")

if __name__ == "__main__":
    main()

You can run this script with the --help flag to see the description and usage.

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9. Subcommands for CLI

import argparse

def create(args):
    print(f"Creating resource with name: {args.name}")

def delete(args):
    print(f"Deleting resource with name: {args.name}")

def main():
    parser = argparse.ArgumentParser(description="A CLI with subcommands")
    subparsers = parser.add_subparsers()

    # Subcommand 'create'
    create_parser = subparsers.add_parser("create", help="Create a resource")
    create_parser.add_argument("name", help="Name of the resource")
    create_parser.set_defaults(func=create)

    # Subcommand 'delete'
    delete_parser = subparsers.add_parser("delete", help="Delete a resource")
    delete_parser.add_argument("name", help="Name of the resource")
    delete_parser.set_defaults(func=delete)

    args = parser.parse_args()
    args.func(args)

if __name__ == "__main__":
    main()

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10. File Argument Parsing

import argparse

def main():
    parser = argparse.ArgumentParser(description="Read and process a file")
    parser.add_argument("filename", type=str, help="Path to the file")
    args = parser.parse_args()

    with open(args.filename, "r") as file:
        content = file.read()
        print(content)

if __name__ == "__main__":
    main()

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These examples demonstrate how to use argparse for different tasks, such as parsing simple arguments, handling default values, and supporting more complex features like subcommands and file input.