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How to Parse Command Line Arguments in Python with argparse

Build a CLI that accepts positional integers, an optional --sum flag, and a --verbose switch, all with Python's standard argparse library.

argparse cli command line

Python

import argparse

def main():
    parser = argparse.ArgumentParser(description='Process some integers.')
    parser.add_argument('numbers', metavar='N', type=int, nargs='+',
                        help='an integer for the accumulator')
    parser.add_argument('--sum', dest='accumulate', action='store_const',
         …

12 0 Open

Functions & basics easy

How to Validate CLI Integer Option Within a Range in Python

Use argparse with integer type and bounds checking to validate a command-line option falls within a specified min-max range.

argparse cli validation

Python

import argparse

def main():
    parser = argparse.ArgumentParser(description="Validate an integer within a range.")
    parser.add_argument("--value", type=int, required=True, help="Integer to validate")
    parser.add_argument("--min", type=int, default=0, help="Minimum allowed value")
    parser.add_argument("--max…

14 0 Open

Functions & basics easy

Write a Recursive Factorial Function in Python

Define a recursive factorial function that handles edge cases and returns the product of all positive integers up to n.

recursion factorial functions

Python

def factorial(n):
    """Return the factorial of n using recursion."""
    if n < 0:
        raise ValueError("Factorial is not defined for negative numbers")
    if n == 0 or n == 1:
        return 1
    return n * factorial(n - 1)

if __name__ == "__main__":
    print(factorial(5))

14 0 Open

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