Python sys Module

The sys module provides access to variables and functions that interact with the Python interpreter itself. It exposes system-specific parameters, the module search path, and standard I/O streams.

Use Cases:
- Accessing command-line arguments
- Modifying the module search path at runtime
- Checking Python version information
- Controlling the recursion limit
- Redirecting standard input, output, and error streams

Example 1: Command-line argument handling
    import sys

    if len(sys.argv) < 2:
        print(f"Usage: {sys.argv[0]} <filename>", file=sys.stderr)
        sys.exit(1)

    filename = sys.argv[1]
    print(f"Processing: {filename}")
    print(f"Python version: {sys.version}")
    print(f"Platform: {sys.platform}")

Example 2: Checking object sizes and recursion
    import sys

    data = {"key": "value", "numbers": list(range(100))}
    print(f"Dict size: {sys.getsizeof(data)} bytes")
    print(f"List size: {sys.getsizeof(data['numbers'])} bytes")
    print(f"Recursion limit: {sys.getrecursionlimit()}")

    # Increase recursion limit for deep algorithms
    sys.setrecursionlimit(5000)

Key attributes include sys.argv (command-line arguments), sys.path (module search path), sys.stdin/stdout/stderr (I/O streams), sys.version (Python version string), sys.platform (OS identifier), and sys.modules (cached imported modules). For serious CLI applications, the argparse module is preferred over raw sys.argv.