Question 1

What is a generator in Python and how is it different from a regular function?

Accepted Answer

A generator uses 'yield' to produce values lazily one at a time, pausing execution between calls — enabling memory-efficient iteration. def gen(): yield 1; yield 2. Each call to next() resumes from where it left off. Generators are memory-efficient for large sequences since they don't compute all values upfront.

Question 2

What is the difference between @classmethod and @staticmethod in Python?

Accepted Answer

@classmethod receives the class (cls) as first argument; @staticmethod receives no implicit argument — it's a plain function inside the class namespace. @classmethod: used for factory methods and accessing class state via cls. @staticmethod: utility function that doesn't need class or instance state. Neither requires an instance to call.

Question 3

What is Python's GIL and how does it affect multi-threaded programs?

Accepted Answer

The Global Interpreter Lock prevents multiple native threads from executing Python bytecode simultaneously — limiting CPU parallelism in CPython. Due to the GIL, CPU-bound threads don't run in true parallel. For CPU parallelism, use multiprocessing. For I/O-bound concurrency (network, disk), threads or asyncio work fine since I/O releases the GIL.

Question 4

What are Python's dunder (magic) methods?

Accepted Answer

Special methods with double underscores (__init__, __str__, __len__) that define how objects behave with built-in operations. __init__: constructor. __str__: str(obj). __len__: len(obj). __eq__: obj == other. __add__: obj + other. Implementing them lets your objects integrate naturally with Python's syntax and built-in functions.

Question 5

What is the difference between '==' and 'is' in Python?

Accepted Answer

'==' compares values (equality); 'is' compares object identity (same memory address). a = [1,2]; b = [1,2]. a == b is True (same content). a is b is False (different objects). Always use '==' to compare values. Use 'is' only to check for None (e.g., if x is None).

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