///

## About "Form Fields" { #about-form-fields }

The way HTML forms (`<form></form>`) sends the data to the server normally uses a "special" encoding for that data, it's different from JSON.

**FastAPI** will make sure to read that data from the right place instead of JSON.

/// note | Technical Details

Data from forms is normally encoded using the "media type" `application/x-www-form-urlencoded`.

# Request Forms and Files { #request-forms-and-files }

You can define files and form fields at the same time using `File` and `Form`.

/// info

To receive uploaded files and/or form data, first install <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">`python-multipart`</a>.

Make sure you create a [virtual environment](../virtual-environments.md){.internal-link target=_blank}, activate it, and then install it, for example:

Using `UploadFile` has several advantages over `bytes`:

* You don't have to use `File()` in the default value of the parameter.
* It uses a "spooled" file:
    * A file stored in memory up to a maximum size limit, and after passing this limit it will be stored in disk.
* This means that it will work well for large files like images, videos, large binaries, etc. without consuming all the memory.
* You can get metadata from the uploaded file.

Now, when the clients **create a new hero**, they will send the `secret_name`, it will be stored in the database, but those secret names won't be returned in the API to the clients.

/// tip

This is how you would handle **passwords**. Receive them, but don't return them in the API.

You would also **hash** the values of the passwords before storing them, **never store them in plain text**.

///

The fields of `HeroCreate` are:

  html_url: https://github.com/fastapi/full-stack-fastapi-template
  stars: 37341
  owner_login: fastapi
  owner_html_url: https://github.com/fastapi
- name: Hello-Python
  html_url: https://github.com/mouredev/Hello-Python
  stars: 31799
  owner_login: mouredev
  owner_html_url: https://github.com/mouredev
- name: serve
  html_url: https://github.com/jina-ai/serve
  stars: 21721
  owner_login: jina-ai

# Lifespan Events { #lifespan-events }

You can define logic (code) that should be executed before the application **starts up**. This means that this code will be executed **once**, **before** the application **starts receiving requests**.

The same way, you can define logic (code) that should be executed when the application is **shutting down**. In this case, this code will be executed **once**, **after** having handled possibly **many requests**.

* (Optionally) use `PATCH` instead of `PUT`.
* Retrieve the stored data.
* Put that data in a Pydantic model.
* Generate a `dict` without default values from the input model (using `exclude_unset`).
    * This way you can update only the values actually set by the user, instead of overriding values already stored with default values in your model.

    @Timeout(5)
    public void testSessionLifecycle() throws Exception {
        SmbSessionImpl session = new SmbSessionImpl(mockContext, "testhost", "testdomain", mockTransport);

        // Test initial state - session starts with usage count > 0 due to transport.acquire()
        assertTrue(session.isInUse(), "New session should be in use due to transport acquisition");

        // Test additional acquire
        session.acquire();

And be compatible with all of them at the same time.

///

Create a utility function to hash a password coming from the user.

And another utility to verify if a received password matches the hash stored.

And another one to authenticate and return a user.

{* ../../docs_src/security/tutorial004_an_py310.py hl[8,49,56:57,60:61,70:76] *}

/// note

///

/// note

This is supported since FastAPI version `0.113.0`. 🤓

///

## Pydantic Models for Forms { #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`:

{* ../../docs_src/request_form_models/tutorial001_an_py39.py hl[9:11,15] *}