10 Python Interview Questions (Pune Freshers, 2026)

The list

1. 1

   What's the difference between a list, a tuple, and a set in Python?

   List: mutable, ordered, allows duplicates, uses []. Tuple: immutable, ordered, allows duplicates, uses (). Set: mutable, unordered, no duplicates, uses {}. Performance: sets give O(1) membership check vs lists' O(n).

   Why it matters: Asked at ~85% of Pune Python fresher rounds. Mention NamedTuple + dataclass(frozen=True) as senior-fresher signals.

   Best for: First-pass language fundamentals screening.

2. 2

   Explain Python's mutable vs immutable types.

   Immutable (int, float, str, tuple, frozenset) — cannot be changed after creation; operations create new objects. Mutable (list, dict, set, bytearray) — can be modified in place. Practical impact: immutables are safe as dict keys + thread-safe; mutables aren't.

   Why it matters: Asked at ~70% of Pune rounds. Common follow-up: 'why is `def f(x=[]):` an anti-pattern?' (mutable default — shared across all calls).

   Best for: Demonstrating Python mental model depth.

3. 3

   What's the difference between deep copy and shallow copy?

   Shallow copy (copy.copy or list[:]) duplicates the outer container but inner references stay shared. Deep copy (copy.deepcopy) recursively duplicates everything. Test with a nested list — modify an inner element in the shallow copy, see it change in the original; not so for deep copy.

   Why it matters: Asked at ~55% of Pune rounds. Common gotcha: '=' is NEITHER shallow NOR deep — it's a reference binding.

   Best for: Memory model + reference semantics question.

4. 4

   Explain list comprehensions with an example.

   Concise syntactic way to build a list by applying an expression to each element of an iterable, optionally filtered. Syntax: [expression for item in iterable if condition]. Example: [x*x for x in range(10) if x % 2 == 0] = squares of even numbers. Sister comprehensions for sets {} and dicts {k: v for ...}.

   Why it matters: Asked at ~75% of Pune rounds. Mention generator expressions ((x*x for x in range(10))) for memory efficiency on large iterables.

   Best for: Pythonic-idioms screen; expected fluency.

5. 5

   What's a decorator and when would you use one?

   A decorator is a function that takes another function and extends its behaviour without modifying its source code. Common use cases: logging, timing, caching (@lru_cache), authentication (@login_required), retry logic. Implementation: a wrapper function that calls the original. Pattern: `def decorator(func): def wrapper(*args, **kwargs): ... return wrapper`.

   Why it matters: Asked at ~60% of Pune rounds. Walk through writing a @timer decorator on the whiteboard if asked.

   Best for: Higher-order function understanding; common Django middleware question.

6. 6

   What's the difference between a list and a generator?

   List stores all elements in memory; generator produces elements lazily one at a time. Generators use yield in a function or generator expressions ((x for x in range(10))). Trade-off: lists can be iterated multiple times; generators only once. Use generators for large/infinite sequences where memory matters.

   Why it matters: Asked at ~50% of Pune rounds, especially data + AI tracks. Mention itertools as a standard-library source of generator-based utilities.

   Best for: Memory + iteration semantics; common data-pipeline question.

7. 7

   Explain *args and **kwargs.

   *args collects positional arguments as a tuple; **kwargs collects keyword arguments as a dict. Pattern: `def my_func(*args, **kwargs):`. Used for flexible function signatures + forwarding to another function (`other_func(*args, **kwargs)`). The names are convention — you can use *positional / **keyword names but stick with the convention.

   Why it matters: Asked at ~55% of Pune rounds. Common follow-up: 'forwarding kwargs to a function that doesn't accept them' (use **kwargs unpacking + signature inspection).

   Best for: Function-signature flexibility question.

8. 8

   What is the GIL (Global Interpreter Lock)?

   CPython's mechanism that allows only one thread to execute Python bytecode at a time. Implication: pure-Python multithreading doesn't give CPU-bound speedup (use multiprocessing instead). Threads are still useful for I/O-bound work (network calls, file I/O) where the GIL is released during system calls.

   Why it matters: Asked at ~45% of Pune rounds, especially product company + backend tracks. Mention Python 3.13+ optional no-GIL build as cutting-edge awareness.

   Best for: Concurrency understanding; differentiates beyond services-major tier.

9. 9

   What's the difference between __init__ and __new__ in a class?

   __new__ creates and returns the new instance (rarely overridden; mostly relevant for immutable types or metaclasses). __init__ initialises the already-created instance (set attributes, validate state) and returns None. The flow: __new__ runs first, then __init__ on the returned instance.

   Why it matters: Asked at ~30% of Pune rounds, mostly product company + OOP-focused interviews. Often a follow-up to 'design a Singleton in Python' — use __new__ to return the same instance every time.

   Best for: OOP depth + design-pattern signal.

10. 10

    How does Python handle errors? Explain try/except/finally/else.

    try wraps risky code; except catches specific exceptions; else runs if no exception was raised; finally always runs (cleanup, releasing resources). Practical use: catch specific exception types (ValueError, IOError) rather than bare except. Modern Python uses context managers (`with open(...) as f:`) for cleanup rather than try/finally.

    Why it matters: Asked at ~50% of Pune rounds. Common follow-up: 'create a custom exception' — subclass Exception or a more specific built-in.

    Best for: Error-handling discipline screen.

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