These 64 Python Full Stack questions answer common beginner questions about Python, Django, APIs and Deployment. Use the topic links to find a short explanation, then try the practice exercise to apply it.
Explore the ScholarLogic Python Full Stack course in Bengaluru, based in BTM Layout, or try the beginner practice exercise.
Python fundamentals
How does Python indentation affect code?
It defines blocks. Use consistent indentation and align statements that belong to the same block.
What does None represent in Python?
It is a single object commonly used to represent an absent value. Use is None for an identity check.
When should I use a Python set?
Use it for unique hashable items or membership checks. Use a list when duplicates or sequence positions matter.
What is slicing in Python?
It selects part of a sequence using start, stop and step. The stop position is excluded.
Why use enumerate in a Python loop?
It yields each item with a counter, so you can use positions without incrementing a separate variable.
How does zip pair Python iterables?
It pairs corresponding items. By default it stops when the shortest iterable runs out.
Why can a mutable default argument cause a bug?
Python evaluates defaults once when defining the function. Use None and create a fresh list inside the function.
What is a generator in Python?
It produces items lazily as you iterate. This is useful when the complete result need not be held in memory.
When do I need a shallow copy of a list?
Use it for a new outer list. Nested mutable objects are still shared.
What do Python type hints do?
They document expected types and help static checkers. Python generally does not enforce them at runtime.
What is a Python dataclass useful for?
It can generate common methods for a class holding data. Add validation explicitly when needed.
How should a Python app join filesystem paths?
Use pathlib Path operations so separator handling works across platforms.
How do I read a large text file in Python?
Open it with a context manager and iterate one line at a time. Specify the encoding when you know it.
Why catch a specific Python exception?
A targeted handler can recover from a known failure while letting unrelated programming errors surface.
What is a Python module entry point?
A conditional check for __name__ equal to __main__ lets script-only code run when the module is executed directly.
How should I record dependencies for deployment?
Declare versions in project metadata and use a reproducible lock or pinned install for the target environment.
Django application design
How does Django match a browser URL?
It checks URL patterns in order and calls the first matching view with any captured values.
Why name a Django URL pattern?
A name lets templates and views build links without hardcoding the path. Use namespaces for reusable apps.
What is Django template inheritance?
A base template defines blocks and a child fills them, so shared navigation and layout stay in one place.
Why does Django escape template variables?
Escaping prevents ordinary data from being treated as HTML. Only render trusted content as safe.
How do I render user-entered multiline text safely?
Keep HTML escaping enabled and use presentation rules to preserve whitespace as needed.
What is a Django ModelForm?
It builds form fields from selected model fields and can save validated values. Declare editable fields explicitly.
How do I compare two fields in a Django form?
Use the form clean method after individual fields are processed. Handle the case where an invalid field is absent.
When should I use a Django UniqueConstraint?
Use it when the database must prevent duplicate keys or combinations, including under concurrent writes.
How do I apply related Django writes together?
Use transaction.atomic so the unit commits together or rolls back when an error escapes the block.
Why do Django migrations belong in version control?
They let each environment apply the same schema history and let reviewers see changes before deployment.
What is a Django data migration?
It changes existing data as part of deployment history. Use the historical models supplied to the migration.
How can I add a required column to an existing table?
Stage the change with a compatible column, backfill existing rows, then enforce the required constraint.
How do I page a long list in Django?
Use a paginator with a stable ordering. Decide how to handle invalid or out-of-range page values.
What is Django middleware?
It wraps request and response handling for shared behavior such as sessions or security headers.
Where should a Django app store user uploads?
Use the configured storage backend and validate uploaded files. Keep uploaded content separate from executable application code.
Why configure ALLOWED_HOSTS in Django?
It limits accepted Host header values. List intended deployment hosts rather than opening the setting without reason.
APIs and interfaces
What is a JSON API content type?
Use application/json for JSON request or response bodies. Send data matching the agreed schema.
How should a frontend handle an HTTP 404 response?
Show that the record is unavailable and offer a route back. Handle network failures separately.
How do I prevent duplicate form clicks in React?
Disable the submit control while the request is pending. Use server-side protection where repeated submissions can create duplicates.
What is a controlled React input?
Its displayed value comes from component state and changes through an event handler.
Why do React lists need stable keys?
Keys let React preserve the identity of each item across updates. Use an item ID when available.
How should a React app show loading and empty results?
Render loading, error and empty states separately so users can tell whether a request has finished.
What is CORS in a browser API request?
It is a browser-controlled policy for reading responses across origins. A server opts in for intended origins.
Why is CORS different from API permissions?
CORS controls browser access to cross-origin responses. The server still needs authentication and authorization checks.
When should an API use cursor pagination?
It helps navigate large changing collections. Base the cursor on a stable, deterministic ordering.
What should a filterable API expose?
Document allowed filters, sorts and defaults. Validate inputs and cap result size.
What should a Python API return for invalid form input?
Return a documented client error with field-specific messages. Avoid including private data or internal stack traces.
How do I avoid fetching every database field for a listing?
Select only fields needed for the response where practical. Confirm related access does not add extra queries.
What does an API timeout mean for a submit button?
The client stopped waiting, so success may be unknown. Retry only when duplicates are handled.
Why version an API contract?
Versioning gives clients time to migrate when field meanings or required behavior change incompatibly.
How do I check that an API date is unambiguous?
Use a documented date format. For instants include UTC or an explicit offset.
What should an API error response contain?
Use a stable error identifier and readable message. Include safe field details when the client can correct them.
Testing and deployment
What does a Django test client let me check?
It sends simulated requests through the app and exposes status, redirects and rendered context without running a live server.
How do I test a Django object permission?
Create two users and an object owned by one. Confirm the other user cannot update it and the database remains unchanged.
When should I mock a Python dependency?
Mock costly or unreliable external calls to test app decisions. Keep integration tests for the real contract.
What is a useful test for a database constraint?
Attempt the conflicting write and assert it fails. Also test the valid neighboring case.
How can I check the number of Django queries?
Use query-count assertions on a representative route. Include enough rows to expose queries that grow per item.
Why use environment-specific Python settings?
Production needs different hosts, secrets and logging. Keep shared defaults in one place and make environment choices explicit.
What should DEBUG be in a public Django deployment?
Set DEBUG to False and configure proper error pages. Debug responses can reveal internals.
What is a Django static file?
It is an application asset such as CSS or JavaScript. It differs from media uploaded by users.
What does collectstatic do in Django?
It gathers app assets into the configured static destination so a server or storage backend can serve them.
How do I diagnose a missing CSS file after deployment?
Check the asset URL and status, then inspect the static build and storage configuration.
Why include a health endpoint for a Python service?
It gives monitoring a consistent way to check whether the service is running. Keep it lightweight and free of secrets.
What belongs in a useful Python error log?
Record the error and request context such as a trace ID. Keep credentials and sensitive fields out.
When should a Python web app use a background task?
Move slow, retryable work off the request path. Make the task safe to rerun and monitor failures.
What is a smoke test after deploying Django?
It exercises a few critical routes and checks expected status or content using a safe account or public page.
How do I check a Python app after a database migration?
Run basic reads and writes that depend on the changed schema and inspect migration status.
What should a Django portfolio demo include?
Show one end-to-end user flow, the data model, a security or validation test and reproducible setup instructions.
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