import argparse

What is it? When use it?
Python in-built parser inherited from C language
“argparse” library
How to use “argparse”?
Examples
Resources

What is it? When use it?

The rule of thumb is that, if you want to provide a user-friendly approach to configuring your program, then you should consider a command line interface.
https://docs.python.org/3/library/argparse.html

Python in-built parser inherited from C language

# myls.py
import os
import sys

if len(sys.argv) > 2:
    print('You have specified too many arguments')
    sys.exit()

if len(sys.argv) < 2:
    print('You need to specify the path to be listed')
    sys.exit()

input_path = sys.argv[1]

if not os.path.isdir(input_path):
    print('The path specified does not exist')
    sys.exit()

print('\n'.join(os.listdir(input_path)))

“argparse” library

getopt and optparse are old version of parsers
The Python argparse library:

Allows the use of positional arguments
Allows the customization of the prefix chars
Supports variable numbers of parameters for a single option
Supports subcommands (A main command line parser can use other command line parsers depending on some arguments.)

How to use “argparse”?

Import the Python argparse library
Create the parser
Add optional and positional arguments to the parser
Execute .parse_args()

Examples

‣

1: simple example

‣

2: with subprocess

Resources

Made with Super

"""
How to run: python argparse_example.py --name Rustam --age 20 100 200 --values 1 2 3
1. --name is a required arg (flag)
2. x, y are positional arguments
3. --age is an optional argument
4. Multiple Input Arguments
5. Mutually Exclusive Arguments, depending on one argument, you want to restrict the use of another.
6. Subparser
https://towardsdatascience.com/a-simple-guide-to-command-line-arguments-with-argparse-6824c30ab1c3
"""

import argparse

# Create the parser
parser = argparse.ArgumentParser()

# Add an argument
parser.add_argument('--name', type=str, required=True)
parser.add_argument('--age', type=int)
parser.add_argument('x', type=int, help='The first value to multiply')
parser.add_argument('y', type=int, help='The second value to multiply')
parser.add_argument('--values', type=int, nargs=3)  # Multiple Input Arguments, nargs='+

# Parse the argument
args = parser.parse_args()

sum_ = sum(args.values)

# Print "Hello" + the user input argument
print('Checking...', args.name)

if args.age:
    print(args.name, 'is', args.age, 'years old.')
else:
    print('Hello,', args.name + '!')

print('Multiplication:', args.x * args.y)
print('Sum:', sum_)
Footer

"""
python user.py login --username D0loresh4ze --password whoismrrobot
python user.py register --firstname Dolores --lastname Haze --username Doloresh4ze --email dhaze@ecorp.com --password whoismrrobot
"""

import argparse

parser = argparse.ArgumentParser()
subparser = parser.add_subparsers(dest='command')

login = subparser.add_parser('login')
register = subparser.add_parser('register')

login.add_argument('--username', type=str, required=True)
login.add_argument('--password', type=str, required=True)

register.add_argument('--firstname', type=str, required=True)
register.add_argument('--lastname', type=str, required=True)
register.add_argument('--username', type=str, required=True)
register.add_argument('--email', type=str, required=True)
register.add_argument('--password', type=str, required=True)

args = parser.parse_args()

if args.command == 'login':
    print('Logging in with username:', args.username,
          'and password:', args.password)
elif args.command == 'register':
    print('Creating username', args.username,
          'for new member', args.firstname, args.lastname,
          'with email:', args.email,
          'and password:', args.password)