Basic query parameter declaration in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a query parameter in FastAPI?

A query parameter is a value sent in the URL after a question mark (?) that the server can read and use. In FastAPI, you declare it as a function parameter in your path operation function.

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How do you declare a basic query parameter in FastAPI?

You add a function parameter with a default value or type annotation in your path operation function. For example: <br>def read_item(q: str = None): declares a query parameter named 'q'.

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What happens if you don't provide a default value for a query parameter in FastAPI?

FastAPI treats it as a required query parameter. The client must send it in the URL, or FastAPI will return an error.

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Example: What does this FastAPI function do?<br>@app.get('/items/')<br>def read_items(q: str = None):<br> return {'q': q}

It declares a GET endpoint '/items/' that accepts an optional query parameter 'q'. If 'q' is sent in the URL, it returns it in a dictionary. If not sent, it returns {'q': None}.

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Why use query parameters instead of path parameters?

Query parameters are good for optional or filtering data without changing the URL structure. Path parameters are for required parts of the URL that identify a resource.

How do you declare an optional query parameter named 'search' in FastAPI?

A def read(search: str = None):

B def read(search: str):

C def read(search):

D def read(search: int = 0):

Declaring with a default value None makes the query parameter optional.

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

A FastAPI returns an error response.

B FastAPI uses a default value.

C FastAPI ignores the parameter.

D FastAPI crashes.

FastAPI expects required query parameters and returns an error if missing.

Which symbol starts query parameters in a URL?

A &

B #

C ?

D /

Query parameters start after a question mark (?) in the URL.

In FastAPI, how do you access the value of a query parameter inside your function?

A Using request.body().

B By declaring a function parameter with the same name.

C Using global variables.

D Using environment variables.

FastAPI matches query parameters to function parameters by name.

Which of these is a valid query parameter declaration in FastAPI?

A def get_items(limit):

B def get_items():

C def get_items(limit: str):

D def get_items(limit: int = 10):

Declaring with a default value and type is valid and makes the parameter optional.

Explain how to declare and use a basic query parameter in FastAPI.

Think about how the function parameter relates to the URL query string.

Describe the difference between required and optional query parameters in FastAPI.

Consider what happens if the client does not send the parameter.