starlette/docs/requests.md

Starlette includes a `Request` class that gives you a nicer interface onto
the incoming request, rather than accessing the ASGI scope and receive channel directly.

### Request

Signature: `Request(scope, receive=None)`

```python
from starlette.requests import Request
from starlette.responses import Response


class App:
    def __init__(self, scope):
        assert scope['type'] == 'http'
        self.scope = scope

    async def __call__(self, receive, send):
        request = Request(self.scope, receive)
        content = '%s %s' % (request.method, request.url.path)
        response = Response(content, media_type='text/plain')
        await response(receive, send)
```

Requests present a mapping interface, so you can use them in the same
way as a `scope`.

For instance: `request['path']` will return the ASGI path.

If you don't need to access the request body you can instantiate a request
without providing an argument to `receive`.

#### Method

The request method is accessed as `request.method`.

#### URL

The request URL is accessed as `request.url`.

The property is a string-like object that exposes all the
components that can be parsed out of the URL.

For example: `request.url.path`, `request.url.port`, `request.url.scheme`.

#### Headers

Headers are exposed as an immutable, case-insensitive, multi-dict.

For example: `request.headers['content-type']`

#### Query Parameters

Query parameters are exposed as an immutable multi-dict.

For example: `request.query_params['search']`

#### Path Parameters

Router path parameters are exposed as a dictionary interface.

For example: `request.path_params['username']`

#### Client Address

The client's remote address is exposed as a named two-tuple `request.client`.
Either item in the tuple may be `None`.

The hostname or IP address: `request.client.host`

The port number from which the client is connecting: `request.client.port`

#### Cookies

Cookies are exposed as a regular dictionary interface.

For example: `request.cookies.get('mycookie')`

#### Body

There are a few different interfaces for returning the body of the request:

The request body as bytes: `await request.body()`

The request body, parsed as form data or multipart: `await request.form()`

The request body, parsed as JSON: `await request.json()`

You can also access the request body as a stream, using the `async for` syntax:

```python
from starlette.requests import Request
from starlette.responses import Response


class App:
    def __init__(self, scope):
        assert scope['type'] == 'http'
        self.scope = scope

    async def __call__(self, receive, send):
        request = Request(self.scope, receive)
        body = b''
        async for chunk in request.stream():
            body += chunk
        response = Response(body, media_type='text/plain')
        await response(receive, send)
```

If you access `.stream()` then the byte chunks are provided without storing
the entire body to memory. Any subsequent calls to `.body()`, `.form()`, or `.json()`
will raise an error.

In some cases such as long-polling, or streaming responses you might need to
determine if the client has dropped the connection. You can determine this
state with `disconnected = await request.is_disconnected()`.

#### Request Files

Request files are normally sent as multipart form data (`multipart/form-data`).

When you call `await request.form()` you receive a `starlette.datastructures.FormData` which is an immutable
multidict, containing both file uploads and text input. File upload items are represented as instances of `starlette.datastructures.UploadFile`.

`UploadFile` has the following attributes:

* `filename`: A `str` with the original file name that was uploaded (e.g. `myimage.jpg`).
* `content_type`: A `str` with the content type (MIME type / media type) (e.g. `image/jpeg`).
* `file`: A <a href="https://docs.python.org/3/library/tempfile.html#tempfile.SpooledTemporaryFile" target="_blank">`SpooledTemporaryFile`</a> (a <a href="https://docs.python.org/3/glossary.html#term-file-like-object" target="_blank">file-like</a> object). This is the actual Python file that you can pass directly to other functions or libraries that expect a "file-like" object.


`UploadFile` has the following `async` methods. They all call the corresponding file methods underneath (using the internal `SpooledTemporaryFile`).

* `async write(data)`: Writes `data` (`str` or `bytes`) to the file.
* `async read(size)`: Reads `size` (`int`) bytes/characters of the file.
* `async seek(offset)`: Goes to the byte position `offset` (`int`) in the file.
    * E.g., `await myfile.seek(0)` would go to the start of the file.
* `async close()`: Closes the file.

As all these methods are `async` methods, you need to "await" them.

For example, you can get the file name and the contents with:

```python
form = await request.form()
filename = form["upload_file"].filename
contents = await form["upload_file"].read()
```

#### Other state

If you want to store additional information on the request you can do so
using `request.state`.

For example:

`request.state.time_started = time.time()`