Starlette includes a few response classes that handle sending back the
appropriate ASGI messages on the `send` channel.
### Response
Signature: `Response(content, status_code=200, headers=None, media_type=None)`
* `content` - A string or bytestring.
* `status_code` - An integer HTTP status code.
* `headers` - A dictionary of strings.
* `media_type` - A string giving the media type. eg. "text/html"
Starlette will automatically include a Content-Length header. It will also
include a Content-Type header, based on the media_type and appending a charset
for text types, unless a charset has already been specified in the `media_type`.
Once you've instantiated a response, you can send it by calling it as an
ASGI application instance.
```python
from starlette.responses import Response
async def app(scope, receive, send):
assert scope['type'] == 'http'
response = Response('Hello, world!', media_type='text/plain')
await response(scope, receive, send)
```
#### Set Cookie
Starlette provides a `set_cookie` method to allow you to set cookies on the response object.
Signature: `Response.set_cookie(key, value, max_age=None, expires=None, path="/", domain=None, secure=False, httponly=False, samesite="lax")`
* `key` - A string that will be the cookie's key.
* `value` - A string that will be the cookie's value.
* `max_age` - An integer that defines the lifetime of the cookie in seconds. A negative integer or a value of `0` will discard the cookie immediately. `Optional`
* `expires` - Either an integer that defines the number of seconds until the cookie expires, or a datetime. `Optional`
* `path` - A string that specifies the subset of routes to which the cookie will apply. `Optional`
* `domain` - A string that specifies the domain for which the cookie is valid. `Optional`
* `secure` - A bool indicating that the cookie will only be sent to the server if request is made using SSL and the HTTPS protocol. `Optional`
* `httponly` - A bool indicating that the cookie cannot be accessed via JavaScript through `Document.cookie` property, the `XMLHttpRequest` or `Request` APIs. `Optional`
* `samesite` - A string that specifies the samesite strategy for the cookie. Valid values are `'lax'`, `'strict'` and `'none'`. Defaults to `'lax'`. `Optional`
#### Delete Cookie
Conversely, Starlette also provides a `delete_cookie` method to manually expire a set cookie.
Signature: `Response.delete_cookie(key, path='/', domain=None)`
### HTMLResponse
Takes some text or bytes and returns an HTML response.
```python
from starlette.responses import HTMLResponse
async def app(scope, receive, send):
assert scope['type'] == 'http'
response = HTMLResponse('Hello, world!
')
await response(scope, receive, send)
```
### PlainTextResponse
Takes some text or bytes and returns a plain text response.
```python
from starlette.responses import PlainTextResponse
async def app(scope, receive, send):
assert scope['type'] == 'http'
response = PlainTextResponse('Hello, world!')
await response(scope, receive, send)
```
### JSONResponse
Takes some data and returns an `application/json` encoded response.
```python
from starlette.responses import JSONResponse
async def app(scope, receive, send):
assert scope['type'] == 'http'
response = JSONResponse({'hello': 'world'})
await response(scope, receive, send)
```
#### Custom JSON serialization
If you need fine-grained control over JSON serialization, you can subclass
`JSONResponse` and override the `render` method.
For example, if you wanted to use a third-party JSON library such as
[orjson](https://pypi.org/project/orjson/):
```python
from typing import Any
import orjson
from starlette.responses import JSONResponse
class OrjsonResponse(JSONResponse):
def render(self, content: Any) -> bytes:
return orjson.dumps(content)
```
In general you *probably* want to stick with `JSONResponse` by default unless
you are micro-optimising a particular endpoint or need to serialize non-standard
object types.
### RedirectResponse
Returns an HTTP redirect. Uses a 307 status code by default.
```python
from starlette.responses import PlainTextResponse, RedirectResponse
async def app(scope, receive, send):
assert scope['type'] == 'http'
if scope['path'] != '/':
response = RedirectResponse(url='/')
else:
response = PlainTextResponse('Hello, world!')
await response(scope, receive, send)
```
### StreamingResponse
Takes an async generator or a normal generator/iterator and streams the response body.
```python
from starlette.responses import StreamingResponse
import asyncio
async def slow_numbers(minimum, maximum):
yield ''
for number in range(minimum, maximum + 1):
yield '- %d
' % number
await asyncio.sleep(0.5)
yield '
'
async def app(scope, receive, send):
assert scope['type'] == 'http'
generator = slow_numbers(1, 10)
response = StreamingResponse(generator, media_type='text/html')
await response(scope, receive, send)
```
Have in mind that file-like objects (like those created by `open()`) are normal iterators. So, you can return them directly in a `StreamingResponse`.
### FileResponse
Asynchronously streams a file as the response.
Takes a different set of arguments to instantiate than the other response types:
* `path` - The filepath to the file to stream.
* `headers` - Any custom headers to include, as a dictionary.
* `media_type` - A string giving the media type. If unset, the filename or path will be used to infer a media type.
* `filename` - If set, this will be included in the response `Content-Disposition`.
* `content_disposition_type` - will be included in the response `Content-Disposition`. Can be set to "attachment" (default) or "inline".
File responses will include appropriate `Content-Length`, `Last-Modified` and `ETag` headers.
```python
from starlette.responses import FileResponse
async def app(scope, receive, send):
assert scope['type'] == 'http'
response = FileResponse('statics/favicon.ico')
await response(scope, receive, send)
```
File responses also supports [HTTP range requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_requests).
The `Accept-Ranges: bytes` header will be included in the response if the file exists. For now, only the `bytes`
range unit is supported.
If the request includes a `Range` header, and the file exists, the response will be a `206 Partial Content` response
with the requested range of bytes. If the range is invalid, the response will be a `416 Range Not Satisfiable` response.
## Third party responses
#### [EventSourceResponse](https://github.com/sysid/sse-starlette)
A response class that implements [Server-Sent Events](https://html.spec.whatwg.org/multipage/server-sent-events.html). It enables event streaming from the server to the client without the complexity of websockets.