Numeric validation (gt, lt, ge, le) in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does gt mean in FastAPI numeric validation?

gt means 'greater than'. It ensures the number is strictly more than the given value.

beginner

How do you enforce a number to be less than or equal to 10 in FastAPI?

Use le=10 in the parameter declaration to allow numbers up to 10, including 10.

intermediate

What is the difference between ge and gt in FastAPI validation?

ge means 'greater than or equal to', allowing the number to be equal to the limit.<br>gt means 'greater than', excluding the limit itself.

beginner

Show a FastAPI example that validates an integer query parameter to be between 1 and 5 inclusive.

<pre>from fastapi import FastAPI, Query

app = FastAPI()

@app.get("/items/")
async def read_items(q: int = Query(..., ge=1, le=5)):
    return {"q": q}</pre>

beginner

What happens if a client sends a number outside the allowed range in FastAPI numeric validation?

FastAPI returns a clear error response with status code 422 and a message explaining the validation failure.

In FastAPI, which keyword ensures a number is strictly less than 10?

A le=10

B gt=10

C lt=10

D ge=10

lt=10 means less than 10, excluding 10 itself.

What does ge=5 mean in FastAPI validation?

A Number must be greater than or equal to 5

B Number must be less than or equal to 5

C Number must be less than 5

D Number must be greater than 5

ge=5 means the number can be 5 or more.

Which FastAPI validation keyword would you use to allow numbers up to and including 100?

A le=100

B lt=100

C gt=100

D ge=100

le=100 means less than or equal to 100.

If you want a number strictly greater than 0, which validation keyword do you use?

A ge=0

B le=0

C lt=0

D gt=0

gt=0 means the number must be more than 0, not equal.

What status code does FastAPI return when numeric validation fails?

A 404

B 422

C 200

D 500

FastAPI returns 422 Unprocessable Entity for validation errors.

Explain how to use FastAPI numeric validation keywords to restrict a query parameter between 10 and 20 inclusive.

Think about how to set minimum and maximum limits including the limits themselves.

Describe the difference between gt and ge in FastAPI numeric validation and when you might use each.

Consider if the boundary number should be allowed or not.