Python, argument parameter error with sys module

Question

I am trying to get arguments in python with the sys module. Here my code:

import sys
import os
path = sys.argv[0]
argument = sys.argv[1]
print("Hello, Temal Script installed.")
if argument == "-h":
    os.system("cls")
    print("Available comamnds:\n-h = help\n-i = information\n-v = version")
if argument == "-i":
    os.system("cls")
    print("This is a script written by Temal")
if argument == "-v":
    os.system("cls")
    print("Version: 1.0")

If I enter in the cmd "main.py -h" it works great. But if I enter only "main.py" it prints me out an error:

Traceback (most recent call last):
  File "C:\Windows\cmd.py", line 5, in <module>
    argument = sys.argv[1]
IndexError: list index out of range

I know why i get this error, because in the list will be only one item (the path) because i dont enter a second argument. But how can I do that the script ignores this error if no second argument is set? If someone enters main.py without an argument I only want to print out this text: Hello, Temal Script installed. Or maybe is there something like in PHP "isset"? I am also new to this topic so please answer simple and not complicated. Thanks!

Answer 1

Need to check the length of the sys.argv variable.

import sys
import os

path = sys.argv[0]
if len(sys.argv) > 1:
    argument = sys.argv[1]
    print("Hello, Temal Script installed.")
    if argument == "-h":
        os.system("cls")
        print("Available comamnds:\n-h = help\n-i = information\n-v = version")
    elif argument == "-i":
       os.system("cls")
       print("This is a script written by Temal")
    elif argument == "-v":
        os.system("cls")
        print("Version: 1.0")

Also, look at argparse module.

import argparse
import os

parser = argparse.ArgumentParser(description="My App")
parser.add_argument('-i', '--info', action='store_true',
    help="show information")
parser.add_argument('-v', '--version', action='store_true',
    help="show version")
args = parser.parse_args()

if args.info:
    os.system("cls")
    print("This is a script written by Temal")
elif args.version:
    os.system("cls")
    print("Version: 1.0")

Run main.py -h outputs:

usage: help.py [-h] [-i] [-v]

My App

optional arguments:
  -h, --help     show this help message and exit
  -i, --info     show information
  -v, --version  show version