Simple example of a command line interface for Python using argparse and colorama

command_line_interface.py

#!/usr/bin/env python3
'''
Pretty Command Line Interface Example v1.1
@author: Alexander VanTol
'''

import sys
import traceback
import argparse
from colorama import init, Fore, Back, Style

def main():
    # Initialize the colorma colored command line output
    init()

    # Parse arguments into script. Note that 1st argument is script name
    args = parse_args(sys.argv[1:])

    print_header()

    # Arguments can be accessed via their names as defined in the add_argument
    # method of ArgumentParser
    print('You entered:')
    for item in args.required:
        print(Fore.GREEN + '"' + item + '"')
    print(Fore.RESET + 'as the required argument(s).\n')

    # User supplied optional argument to command line
    if args.optional:
        # Argument must be accessed by full name
        print('You entered ' + Fore.GREEN + '"' + args.optional + '"' +
              Fore.RESET + ' as an optional argument.\n')

    # User supplied force error argument to command line
    if args.error_force:
        try:
            print(Back.LIGHTRED_EX + Fore.BLACK + 'Forcing error...' +
                  Back.RESET + Fore.RESET + '\n')
            impossible = 5 / 0
            print(impossible)
        except Exception:
            print_error('You can print a custom message here.\n')
            # Force exit
            sys.exit()

    print_footer()

def parse_args(args):
    """
    Returns parsed and validated arguments that were passed into the script.

    :param args: The arguments passed into the script
    """
    # Parse arguments from command line
    parser = argparse.ArgumentParser()

    # Add a new required argument(s) with display of r in help. Remove nargs
    # argument if multiple entries not allowed. Only requires a single entry,
    # but user can enter multiple
    parser.add_argument('required', metavar='r', type=str, nargs='+',
                        help='At least one argument is required')

    # Define an optional command line argument that accepts a value
    parser.add_argument('-o', '--optional', help='This argument is optional')

    # Define an optional command line argument that does not accept a value
    parser.add_argument('-e', '--error_force', help='Intentionally cause error',
                        action='store_true')

    return parser.parse_args()

def print_header():
    """
    Print header of tool into command line.
    """
    print(Style.BRIGHT + '\n--------------------------------------------------'
          + '------------------------------')
    print('   COMMAND LINE INTERFACE EXAMPLE')
    print('-------------------------------------------------------------------'
          + '-------------\n' + Style.RESET_ALL)

def print_footer():
    """
    Print footer of tool into command line.
    """
    print(Style.BRIGHT + '\n--------------------------------------------------'
          + '------------------------------')
    print('   END')
    print('-------------------------------------------------------------------'
          + '-------------\n' + Style.RESET_ALL)

def print_error(error=None):
    """
    Print an error into command line with traceback.

    :param error: Optional string to print before traceback
    """
    print(Fore.RED + Style.BRIGHT + '!!!--------------------------------------'
          + '------------------------------------!!!\n')

    if error is not None:
        print(error + '\n')

    traceback.print_exc()

    print('\n!!!--------------------------------------------------------------'
          + '------------!!!' + Style.RESET_ALL + '\n')

if __name__ == '__main__':
    main()