Python interview questions and answers

LocMemCache is an in-process dict, useful for development only.

Celery is a distributed task queue.

A request thread should return quickly

itertools is a standard-library toolkit of fast, memory-efficient iterators.

count(start=0, step=1) yields an infinite arithmetic sequence.

asyncio is Python's built-in library for cooperative concurrent I/O using the event loop.

async def defines a coroutine function.

copy.copy duplicates the outer container but shares nested objects.

sys.getsizeof returns the size of the object itself, not nested containers.

The GIL is a mutex in CPython that allows only one thread to execute Python bytecode at a time.

Dicts locate entries by hash then equality, so a key must implement a stable __hash__ and __eq__.

A dict is flexible but typo-prone and has no field documentation.

CPython ints are arbitrary-precision

The default object is created once, at function definition, and shared across calls.

CPU-bound threads compete for the GIL, so they rarely use more than one core for Python bytecode.

Threads help when they spend time in I/O or in C code that releases the GIL, such as reading sockets, waiting on a database driver, or compressing in zlib.

threading shares one process and one GIL, so CPU-bound Python does not parallelize.

Use a nested factory: the outer function takes decorator arguments and returns the real decorator, which returns the wrapper.

If a class implements __init__ to receive the function and __call__ to run the wrapper, instances are callable decorators.