Python Coding Interview Questions for India 2026

Fundamentals tested at every level: Python data types: int, float, str (immutable), list (mutable ordered), tuple (immutable ordered), dict (mutable key-value, ordered since Python 3.7+), set (mutable unordered unique). Mutable vs immutable: lists and dicts are mutable (can be changed in-place), strings and tuples are immutable (operations return new objects). Pass by assignment: Python passes object references. Mutables can be modified inside functions; reassignment does not affect the caller. List vs tuple: use tuples for fixed collections (coordinates, RGB values), lists for dynamic collections. dict.get(key, default) vs dict[key]: get() returns default if key missing; [] raises KeyError. Walrus operator (:=) Python 3.8+: while chunk := f.read(8192).

OOP in Python: classes, _init, instance vs class variables, @classmethod (receives class, not instance), @staticmethod (no implicit first arg). Dunder methods: str (human-readable), repr (developer-readable, unambiguous), len, getitem, eq. Inheritance: super() to call parent. Multiple inheritance and MRO (Method Resolution Order): C3 linearisation. Property: @property for getter, @setter for setter: controlled attribute access. Decorators: functions that take a function and return a modified function. Used for logging, timing, caching (functools.lrucache), access control. Generator functions: use yield instead of return. Lazy evaluation: produces values on demand. Memory efficient for large sequences. Generator expressions: (x2 for x in range(1000)) vs list comprehension [x2 for x in range(1000)].

Patterns that appear repeatedly in Python interviews at Indian product companies: Counter from collections: from collections import Counter. Counts hashable objects in one line. Counter(word for word in text.split()). defaultdict: avoids KeyError for missing keys. defaultdict(list) for grouping. heapq: Python min-heap. heapq.nlargest(k, items) for top-k problems. bisect: binary search on sorted lists. sorted() with key: sorted(students, key=lambda s: (-s.grade, s.name)). zip and enumerate: for i, (a, b) in enumerate(zip(list1, list2)). any() and all(): any(x > 0 for x in nums). String methods: join, split, strip, replace, startswith, endswith. f-strings (Python 3.6+): f{name} is faster and cleaner than format() or %.

Async Python: asyncio for concurrent I/O-bound operations. async def defines a coroutine. await suspends execution until the awaitable completes. asyncio.gather() runs coroutines concurrently. Used heavily in: web frameworks (FastAPI), high-throughput microservices, data pipelines with concurrent API calls. Python pitfalls tested in interviews: Mutable default arguments: def append(item, lst=[]) is a bug: default list is shared across calls. Use def append(item, lst=None): if lst is None: lst = []. Late binding closures: variables in lambdas are evaluated at call time, not definition time. GIL (Global Interpreter Lock): Python GIL prevents true multi-threading for CPU-bound work. Use multiprocessing for CPU-bound, asyncio/threading for I/O-bound. Memory leaks: circular references with _del_ methods, large lists kept in module scope.