? Python sys Module

? Quick Overview

The sys module in Python gives you direct access to interpreter-level functions, environment details, command-line arguments, I/O streams, and system-specific parameters.

? Key Concepts

Reading Python version and platform info
Handling command-line arguments with sys.argv
Using standard input/output/error streams
Checking and modifying module search paths
Gracefully exiting Python scripts

? Syntax / Theory

You need to import the module before using any of its properties or functions:

? Import sys Module

import sys
print(sys.version)    # Python version
print(sys.platform)   # OS platform

? Command-Line Arguments

# Save as example.py
import sys
print(sys.argv)  # List of command line arguments

? Standard Input, Output, and Error

sys.stdout.write("Hello World\n")   # Write to standard output
sys.stderr.write("This is an error message\n")   # Write to standard error stream

? Module Search Path

print(sys.path)  # List of directories Python searches for modules

? Exiting Python

sys.exit()      # Exit with default status code 0
sys.exit(1)     # Exit with a custom error code

? Live Output / Explanation

What Happens?

sys.argv returns a list of command-line arguments where index 0 is the script name.
sys.stdout writes text directly to the console.
sys.stderr is typically shown in red in terminals and used for error logging.
sys.path helps you debug module import errors.
sys.exit() stops the script immediately.

? Tips

Use sys.argv to manage command-line tools and scripts.
sys.path is very helpful when debugging import issues.
Terminate scripts gracefully using sys.exit().
You can redirect sys.stdout and sys.stderr to files for logging purposes.

? Try It Yourself

Write a script that prints all command-line arguments except the script name.
Redirect sys.stdout to a file and write some text.
Print Python version and platform using sys.version and sys.platform.
Exit a script with a custom code if a user input condition is not met.