example of writing cli program

nju-cli.py

#!/usr/bin/env python
import argparse
import getpass
import sys
from contextlib import contextmanager
from distutils.util import strtobool


def yes_or_no(question, default='no'):
    """Ask question and wait for yes/no answer.

    Args:
        question (str) - question to ask
        default (str) - default anser; 'yes' or 'no'
    Return:
        bool - whether user answered yes (true) or no (false)
    """
    if default is None:
        prompt = " [y/n] "
    elif default == "yes":
        prompt = " [Y/n] "
    elif default == "no":
        prompt = " [y/N] "
    else:
        raise ValueError("invalid default answer: '%s'" % default)

    while True:
        sys.stdout.write(question + prompt)
        choice = input().lower()
        if default is not None and choice == '':
            return strtobool(default)
        try:
            return strtobool(choice)
        except ValueError:
            sys.stdout.write(
                "Please respond with 'yes' or 'no' " "(or 'y' or 'n').\n"
            )


class NjuConnection:
    def __init__(self, username, password):
        pass

    def login(self):
        pass

    def logout(self):
        pass

    def account_balance(self):
        return 12


@contextmanager
def nju_connection(username, password):
    """NJU connection manager

    Args:
        username (str) - nju account username
        password (str) - nju account password

    Returns:
        NjuConnection - logged connection instance
    """

    conn = NjuConnection(username, password)
    try:
        conn.login()
        yield conn
    finally:
        conn.logout()


def main():
    # define program name and description for --help
    prog = sys.argv[0]
    description = "NJU CLI manager"

    # user argparse to create program arguments/options
    parser = argparse.ArgumentParser(prog=prog, description=description)
    parser.add_argument(
        "-c", "--clean", action='store_true',
        help="clean configuration",
    )

    # parse command line
    options = parser.parse_args()

    # you can easily check options
    if options.clean:
        print("Cleaning configuration.")

    # use standard input for username
    username = input('Username: ')

    # use getpass to hide typed password
    password = getpass.getpass('Password: ')

    if yes_or_no('Save configuration?', default='yes'):
        print("... saving configuration")

    if not yes_or_no('Continue?', default='yes'):
        sys.exit("Aborted by user.")

    # thanks to context manager you don't have to care about login/logout
    # manually
    with nju_connection(username, password) as conn:
        print(f"Account balance: {conn.account_balance()} PLN")


if __name__ == "__main__":
    # all interactive code is wrapped in 'main' functions so you can
    # import cli module to reuse code without side effects
    main()