2 to 5 years of experience - Python developer interview questions and sample answers

1. How does Python handle memory management?

Answer: Python uses an automatic memory management system that includes a private heap where all Python objects and data structures are stored. The memory manager handles allocation, and garbage collection frees unused memory, using reference counting and cyclic garbage collector to detect reference cycles.

2. Explain the difference between shallow copy and deep copy.

Answer: Shallow copy creates a new object but inserts references to the objects found in the original. Deep copy creates a new object and recursively copies all objects found in the original, so changes to nested objects in the copy do not affect the original.

3. What is Python’s Global Interpreter Lock (GIL), and how does it affect multi-threading?

Answer: The GIL ensures only one thread executes Python bytecode at a time, which can be a bottleneck for CPU-bound tasks in multi-threaded programs. For I/O-bound tasks, threads can still run concurrently. To bypass GIL limitations for CPU-bound code, multiprocessing or external libraries in C are often used.

4. How do you optimize a Python codebase for performance?

Answer: I profile code to find bottlenecks, use built-in functions and libraries (like NumPy), avoid unnecessary loops, leverage list comprehensions, use efficient data structures, and sometimes rewrite critical parts in C extensions or use concurrency/multiprocessing.

5. Difference between iterable and iterator in Python?

Answer: An iterable is an object capable of returning its members one at a time, allowing it to be looped over in a for-loop. An iterator is an object representing a stream of data, with methods iter() and next() to access elements one-by-one.

6. How do you manage exceptions in Python?

Answer: Using try-except blocks to catch and handle exceptions gracefully, optionally with else and finally clauses to manage cleanup and normal flow.

7. What are lambda functions?

Answer: Lambda functions are anonymous, inline functions defined with the lambda keyword. They can have any number of arguments but only one expression, often used for short, throwaway functions.

8. How do you handle file operations in Python?

Answer: Using the open() function with modes like r, w, a. The with statement is preferred to ensure files are properly closed after usage, even if exceptions occur.

9. What is the difference between static methods and class methods?

Answer: Static methods don’t receive implicit first arguments and behave like regular functions inside a class namespace. Class methods take cls as the first argument and can modify class state.

10. Describe how you would handle multi-threading and multi-processing in Python.

Answer: Multi-threading is suitable for I/O-bound tasks due to the GIL; multi-processing achieves true parallelism for CPU-bound tasks by spawning separate processes with independent memory space.

These answers reflect maturity in Python features and real-world understanding expected from 2-5 years experienced developers, highlighting optimization, concurrency, and advanced Python semantics.