Accepting User Input

Accepting Command Line Arguments

To accept basic arguments from the command line, we can use sys.argv. argv is a list that gets passed in to your program that contains whatever arguments your program was started with. Start a new Python file called cli_exercise.py and enter the following:

import sys

args = sys.argv

print(args)

Now run it:

(env) $ python cli_exercise.py
['cli_exercise.py']

You should see a list with one item: the name of your program. Pass in additional arguments by adding them after your program name on the command line, separated by spaces:

python cli_exercise.py argument1 argument2 "hello world"
['cli_exercise.py', 'argument1', 'argument2', 'hello world']

Note that the name of the file you’re running is rarely useful, so it’s common to see this omitted with using slices, for example sys.argv[1:]

sys.argv is never empty - the first element in the list will always be the name of the Python file you’re running.

Accepting User Input with input

You can also accept user data inside a running program by using input(). Let’s make a simple interactive command line program that asks for a user’s name and birthday:

name = input("Hello, what is your name? ")

birthday_string = input(f"Hello {name}. Please enter your birthday in MM/DD/YYYY format: ")

print(f"Hello {name}. Your birthday is on {birthday_string}.")

(env) $ python cli_exercise.py
Hello, what is your name? Floyd
Hello Floyd. Please enter your birthday in MM/DD/YYYY format: 01/20/1990
Hello Floyd. Your birthday is on 01/20/1990.