Interview Questions

Lists are mutable (you can change, add, remove items) and use more memory; tuples are immutable and slightly faster, usable as dict keys. Use tuples for fixed collections and lists for changing sequences.

A decorator is a callable that wraps another function to extend its behavior without modifying it, applied with `@decorator` syntax. Common uses: logging, timing, caching (`functools.lru_cache`), access control. They are functions returning functions.

The Global Interpreter Lock allows only one thread to execute Python bytecode at a time, simplifying memory management but limiting CPU-bound multithreading. Use multiprocessing or native extensions for CPU parallelism; threads still help with I/O-bound work.