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Functions & basics

Reusable building blocks — parameters, returns, scope, and clear function design.

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Format CLI help text in Python

Build a readable usage string for a command-line tool, aligning flags and wrapping descriptions with the textwrap module.

cli textwrap formatting

Python

import textwrap


def format_help(command_name: str, description: str, options: list[tuple[str, str]]) -> str:
    """Format CLI help text into a readable usage string."""
    header = f"Usage: {command_name} [OPTIONS]"
    lines = [header, "", description, "", "Options:"]

    for flag, help_text in options:
        …

12 0 Open

Functions & basics easy

How to Add a Dry Run Flag to a Python CLI Command

Build a Python CLI command with a --dry-run flag that previews actions and exits before making real changes.

argparse cli dry-run

Python

import argparse
import sys

def main():
    parser = argparse.ArgumentParser(description="Sample CLI command with dry-run flag")
    parser.add_argument("--name", required=True, help="Name to greet")
    parser.add_argument("--dry-run", action="store_true", dest="dry_run",
                        help="Show what would…

11 0 Open

Functions & basics easy

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',
         …

11 0 Open

Functions & basics easy

How to Use a Dispatch Table in Python (Map Strings to Functions)

Maps string command names to callable functions in a dictionary, then dispatches calls safely with error handling.

dispatch-table dictionary functions

Python

def add(a, b):
    return a + b


def subtract(a, b):
    return a - b


def multiply(a, b):
    return a * b


def divide(a, b):
    if b == 0:
        raise ValueError("Division by zero")
    return a / b


dispatch = {
    "add": add,
    "subtract": subtract,
    "multiply": multiply,
    "divide": divide,
}


def…

13 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…

13 0 Open

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