Sys Module

The sys module gives you direct access to variables and functions that interact closely with the Python interpreter itself, such as command-line arguments, system-specific settings, and controlling how a program exits.

Accessing Command-Line Arguments

When a Python script is run from the terminal with extra arguments, sys.argv captures them as a list, with the first item always being the script's own name.

# script.py
import sys
print(sys.argv)

# Running: python script.py hello 123
# Output: ['script.py', 'hello', '123']

Other Useful sys Features

• sys.exit() - immediately stops the program, optionally with an exit status code
• sys.version - returns the current Python interpreter's version as a string
• sys.path - a list of directories Python searches through when importing modules
• sys.platform - identifies the operating system the script is running on

import sys

print(sys.version)     # e.g. 3.12.1
print(sys.platform)    # e.g. 'linux', 'win32', 'darwin'

if len(sys.argv) < 2:
    print("Missing required argument")
    sys.exit(1)

Coming Up Next

Next, you'll take a closer look at some of Python's most commonly used built-in modules, starting with the os module for working with files and directories.