tiangolo.fastapi/docs/en/docs/tutorial/request-form-models.md

Form Models

You can use Pydantic models to declare form fields in FastAPI.

/// info

To use forms, first install python-multipart.

Make sure you create a virtual environment{.internal-link target=_blank}, activate it, and then install it, for example:

$ pip install python-multipart

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/// note

This is supported since FastAPI version 0.113.0. 🤓

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Pydantic Models for Forms

You just need to declare a Pydantic model with the fields you want to receive as form fields, and then declare the parameter as Form:

//// tab | Python 3.9+

{!> ../../../docs_src/request_form_models/tutorial001_an_py39.py!}

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//// tab | Python 3.8+

{!> ../../../docs_src/request_form_models/tutorial001_an.py!}

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//// tab | Python 3.8+ non-Annotated

/// tip

Prefer to use the Annotated version if possible.

///

{!> ../../../docs_src/request_form_models/tutorial001.py!}

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FastAPI will extract the data for each field from the form data in the request and give you the Pydantic model you defined.

Check the Docs

You can verify it in the docs UI at /docs:

Forbid Extra Form Fields

In some special use cases (probably not very common), you might want to restrict the form fields to only those declared in the Pydantic model. And forbid any extra fields.

/// note

This is supported since FastAPI version 0.114.0. 🤓

///

You can use Pydantic's model configuration to forbid any extra fields:

//// tab | Python 3.9+

{!> ../../../docs_src/request_form_models/tutorial002_an_py39.py!}

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//// tab | Python 3.8+

{!> ../../../docs_src/request_form_models/tutorial002_an.py!}

////

//// tab | Python 3.8+ non-Annotated

/// tip

Prefer to use the Annotated version if possible.

///

{!> ../../../docs_src/request_form_models/tutorial002.py!}

////

If a client tries to send some extra data, they will receive an error response.

For example, if the client tries to send the form fields:

• username: Rick
• password: Portal Gun
• extra: Mr. Poopybutthole

They will receive an error response telling them that the field extra is not allowed:

{
    "detail": [
        {
            "type": "extra_forbidden",
            "loc": ["body", "extra"],
            "msg": "Extra inputs are not permitted",
            "input": "Mr. Poopybutthole"
        }
    ]
}

Summary

You can use Pydantic models to declare form fields in FastAPI. 😎