`sys`

The Python sys module provides access to system-specific parameters and functions. It allows you to interact with the Python runtime environment and the underlying operating system.

Here’s a quick example:

Python
      
>>> import sys
>>> sys.version
'3.13.2 (main, Feb 24 2025, 22:41:48) [Clang 16.0.0 (clang-1600.0.26.6)]'

Key Features

Accesses command-line arguments passed to Python scripts
Allows interaction with the Python interpreter
Provides tools to inspect and control the Python runtime
Provides access to standard input, output, and error streams
Provides introspection helpers

Frequently Used Classes and Functions

Object	Type	Description
`sys.argv`	List	Grabs command-line arguments passed to the script
`sys.exit()`	Function	Exits from Python with an optional exit status
`sys.path`	List	Contains directories that the interpreter will search for modules
`sys.version`	`str`	Holds the Python interpreter version information
`sys.stdin`	File-like object	References the standard input stream
`sys.stdout`	File-like object	References the standard output stream
`sys.stderr`	File-like object	References the standard error stream

Examples

Access command-line arguments:

Python
      
>>> import sys
>>> sys.argv
['script.py', 'arg1', 'arg2']

Exit the Python interpreter:

Python
      
>>> import sys
>>> sys.exit(0)

Displays the Python version:

Python
      
>>> import sys
>>> sys.version
'3.13.2 (main, Feb 24 2025, 22:41:48) [Clang 16.0.0 (clang-1600.0.26.6)]'

Common Use Cases

Accessing and processing command-line arguments
Managing the Python path for module imports
Redirecting standard input, output, and error streams
Exiting a program with a specific status code
Introspecting Python code

Real-World Example

Suppose you want to access command-line arguments passed to a Python script. You can do this with sys.argv:

Pythonscript.py
      
    
import sys

if len(sys.argv) > 1:
    print("Arguments passed to the script:")
    for arg in sys.argv[1:]:
        print(arg)
else:
    print("No arguments provided.")

This script checks for command-line arguments and prints them, demonstrating how to use sys to handle command‑line input.

Here’s how the script works:

Shell
      
        
      
    
$ python script.py apple banana cherry
Arguments passed to the script:
apple
banana
cherry

Tutorial

Python Command-Line Arguments

Python command-line arguments are the key to converting your programs into useful and enticing tools that are ready to be used in the terminal of your operating system. In this step-by-step tutorial, you'll learn their origins, standards, and basics, and how to implement them in your program.

intermediate best-practices tools

For additional information on related topics, take a look at the following resources: