Python interview questions and answers

Use inheritance for true is-a relationships and shared polymorphic APIs.

The venv interpreter's sys.prefix points at the env directory, so imports look in venv/lib/site-packages first.

venv ships with Python 3 and is enough for most Django apps.

Editable install links the project into site-packages so code changes apply without reinstalling.

Specifiers such as >=, ~=, and == constrain acceptable versions on a requirement line.

The WSGI/ASGI handler loads middleware, resolves the URL, and calls the view.

Function-based views are clearer for one-off endpoints with simple branching.

A context processor is a function that receives the request and returns a dict merged into every template context.

A child template starts with {% extends 'base.html' %} and fills named {% block %} regions.

select_related performs a SQL join for forward ForeignKey and OneToOne relations and is a single query.

N+1 happens when you fetch a list, then access a related field per row, issuing one query plus N more.

F() references a field value in the database so updates happen in SQL, not in Python.

Q objects let you build complex WHERE clauses with | (OR), & (AND), and ~ (NOT).

Set db_index=True on a field, or declare indexes in Meta.indexes / unique_together / UniqueConstraint.

ForeignKey is many-to-one.

On the way in, Django runs middleware from top to bottom of the MIDDLEWARE list.

Legacy mixin-style middleware implemented process_request, process_view, process_exception, and process_response.

Define a class that takes get_response in __init__ and in __call__ runs pre-logic, calls get_response(request), then post-logic.

It should see the raw request early to apply SSL redirects and refuse bad hosts before other layers do work.

pre_save and pre_delete/post_delete wrap persistence.