Multiple query parameters in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a query parameter in FastAPI?

A query parameter is a key-value pair sent in the URL after a question mark (?). FastAPI reads these to get extra information from the client without changing the URL path.

beginner

How do you define multiple query parameters in a FastAPI endpoint?

You add multiple function parameters with default values or type hints in your path operation function. FastAPI automatically treats them as query parameters.

beginner

Example: How to accept two query parameters 'name' (string) and 'age' (int) in FastAPI?

Use a function like: <br> def read_user(name: str, age: int): <br> FastAPI will expect URLs like ?name=John&age=30.

intermediate

What happens if a required query parameter is missing in a FastAPI request?

FastAPI returns a 422 error (Unprocessable Entity) telling the client that a required query parameter is missing.

beginner

How to make a query parameter optional in FastAPI?

Give the parameter a default value like None. For example: def read_user(name: str = None): means 'name' is optional.

In FastAPI, how do you define multiple query parameters?

A Use path parameters only

B Use a single string parameter with all queries combined

C Define query parameters in a separate config file

D Add multiple function parameters with types in the endpoint function

FastAPI treats function parameters with types as query parameters automatically.

What URL would match this FastAPI endpoint? <br> def read_item(name: str, count: int):

A /items?name=apple&count=5

B /items/apple/5

C /items?apple&5

D /items?count=5

Query parameters are passed after '?' with key=value pairs separated by '&'.

What error does FastAPI return if a required query parameter is missing?

A 500 Internal Server Error

B 404 Not Found

C 422 Unprocessable Entity

D 401 Unauthorized

FastAPI returns 422 when required query parameters are missing or invalid.

How to make a query parameter optional in FastAPI?

A Use a global config

B Give it a default value like None

C Make it a path parameter

D Use a special decorator

Setting a default value makes the parameter optional.

Which of these is NOT a valid way to pass multiple query parameters?

A ?name=John,age=30

B ?name=John&age=30

C ?name=John&city=NY

D ?color=red&size=large

Query parameters must be separated by '&', not commas.

Explain how to handle multiple query parameters in a FastAPI endpoint function.

Think about how function arguments relate to URL query keys.

Describe what happens if a required query parameter is missing in a FastAPI request.

Consider how FastAPI validates input.