Python interview questions and answers

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.

A wrapper calls the original and adds behavior

login_required checks request.user.is_authenticated and redirects or returns 403 depending on configuration.

A list comprehension builds the whole list in memory immediately.

send(value) resumes the generator and makes yield return that value inside the function.

You can yield lines or parsed chunks instead of reading the file into one string or list.

yield from subgen delegates iteration to another iterable or generator, forwarding values, send, and throw.

MRO is the linear order Python uses to find attributes on a class and its bases.

A diamond occurs when two bases share a common ancestor, so a method could be inherited twice.

ABCs, from abc.ABC, let you declare abstract methods that subclasses must implement.

@property turns a method into managed attribute access so callers use obj.x instead of obj.x().