400 Python Interview Questions with Answers 2026

Advanced Internals: Memory management, GIL, multiprocessing, and metaclasses.

Data & Ecosystem: NumPy, Pandas, API integration, and dependency management.

Web & Systems: RESTful design, FastAPI/Flask, authentication, and microservices.

Production Readiness: CI/CD, security best practices, performance profiling, and unit testing.

B) A technique where a nested function references a variable in its capturing scope.

C) A method of closing file streams automatically using the with statement.

D) A specific type of class decorator used to prevent memory leaks.

E) A function that can only be executed once before it is deleted from memory.

F) An internal CPython mechanism used to handle the Global Interpreter Lock.

Correct Answer: B

Overall Explanation: A closure occurs when a nested function references a value in its enclosing scope that is not in its own local scope. This allows the inner function to "remember" the environment in which it was created even after the outer function has finished executing.

Option A: Incorrect; the defining characteristic is that it does have access to outer variables.

Option B: Correct; this is the standard definition of a lexical closure in Python.

Option C: Incorrect; this describes Context Managers, not closures.

Option D: Incorrect; while decorators often use closures, a closure itself is not a class decorator.

Option E: Incorrect; closures can be called multiple times like any other function.

Option F: Incorrect; this is unrelated to the GIL or CPython's threading model.

Question 2: In Python's memory management, what is the primary purpose of the 'Generation' system in the Garbage Collector (GC)?

B) To categorize objects by size so that larger objects are deleted faster.

C) To implement the "Weak Generational Hypothesis" – younger objects are more likely to die.

D) To manage the execution of generator functions using the yield keyword.

E) To ensure that global variables are never cleared from the heap.

F) To bypass the GIL during intensive memory allocation tasks.

Correct Answer: C

Overall Explanation: CPython’s GC uses a generational approach (Generations 0, 1, and 2). It assumes that most objects have short lifespans, so it scans newer objects (Gen 0) more frequently than older ones to improve performance.

Option A: Incorrect; memory addresses are handled by the private heap manager, not the generational GC.

Option B: Incorrect; the system is based on the "age" (survival of GC scans), not the physical size of the object.

Option C: Correct; this hypothesis is the foundation of generational garbage collection.

Option D: Incorrect; this confuses the "Generator" language feature with "Generational" GC.

Option E: Incorrect; global variables can be cleared if their reference count hits zero and they are out of scope.

Option F: Incorrect; the GC is actually subject to the GIL in standard CPython.

Question 3: When using asyncio, what happens if you call a co-routine function without using the await keyword?

B) Python raises a SyntaxError immediately upon execution.

C) The function returns a co-routine object but does not actually run the code inside.

D) The event loop automatically schedules it for the next available cycle.

E) It spawns a new thread to handle the function call in the background.

F) The code executes, but the return value is automatically cast to a Future object.

Correct Answer: C

Overall Explanation: In Python, calling an async def function creates a coroutine object. To actually schedule and run the logic within that coroutine, it must be awaited or managed by an event loop.

Option A: Incorrect; it doesn't execute at all, so it cannot block.

Option B: Incorrect; it is valid syntax to create a coroutine object without awaiting it.

Option C: Correct; the code inside the function body will not trigger until it is awaited.

Option D: Incorrect; you must explicitly use asyncio.create_task() or await to schedule it.

Option E: Incorrect; asyncio is single-threaded; it does not spawn threads automatically.

Option F: Incorrect; it returns a coroutine object, which is distinct from a Future.

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