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< p align = "center" >
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< img width = "320" height = "192" src = "https://raw.githubusercontent.com/encode/starlette/master/docs/starlette.png" alt = 'starlette' >
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< / p >
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< p align = "center" >
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< em > ✨ The little ASGI library that shines. ✨< / em >
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< / p >
< p align = "center" >
< a href = "https://travis-ci.org/encode/starlette" >
< img src = "https://travis-ci.org/encode/starlette.svg?branch=master" alt = "Build Status" >
< / a >
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< a href = "https://codecov.io/gh/encode/starlette" >
< img src = "https://codecov.io/gh/encode/starlette/branch/master/graph/badge.svg" alt = "Coverage" >
< / a >
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< a href = "https://pypi.org/project/starlette/" >
< img src = "https://badge.fury.io/py/starlette.svg" alt = "Package version" >
< / a >
< / p >
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---
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Starlette is a small library for working with [ASGI ](https://asgi.readthedocs.io/en/latest/ ).
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It gives you `Request` and `Response` classes, request routing, a test client, and a
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decorator for writing super-minimal applications.
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**Requirements:**
Python 3.6+
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**Installation:**
```shell
pip3 install starlette
```
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**Example:**
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```python
from starlette import Response
class App:
def __init__ (self, scope):
self.scope = scope
async def __call__ (self, receive, send):
response = Response('Hello, world!', media_type='text/plain')
await response(receive, send)
```
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You can run the application with any ASGI server, including [uvicorn ](http://www.uvicorn.org/ ), [daphne ](https://github.com/django/daphne/ ), or [hypercorn ](https://pgjones.gitlab.io/hypercorn/ ).
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< p align = "center" > — ⭐️ — < / p >
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## Responses
Starlette includes a few response classes that handle sending back the
appropriate ASGI messages on the `send` channel.
### Response
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Signature: `Response(content=b'', 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 or list of pairs of strings.
* `media_type` - A string giving the content type.
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Starlette will automatically include a content-length header. It will also
set the content-type header, including a charset for text types.
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Once you've instantiated a response, you can send it by calling it as an
ASGI application instance.
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```python
class App:
def __init__ (self, scope):
self.scope = scope
async def __call__ (self, receive, send):
response = Response('Hello, world!', media_type='text/plain')
await response(receive, send)
```
### HTMLResponse
Takes some text or bytes and returns an HTML response.
```python
from starlette import HTMLResponse
class App:
def __init__ (self, scope):
self.scope = scope
async def __call__ (self, receive, send):
response = HTMLResponse('< html > < body > < h1 > Hello, world!< / h1 > < / body > < /html')
await response(receive, send)
```
### JSONResponse
Takes some data and returns an `application/json` encoded response.
```python
from starlette import JSONResponse
class App:
def __init__ (self, scope):
self.scope = scope
async def __call__ (self, receive, send):
response = JSONResponse({'hello': 'world'})
await response(receive, send)
```
### StreamingResponse
Takes an async generator and streams the response body.
```python
from starlette import Request, StreamingResponse
import asyncio
async def slow_numbers(minimum, maximum):
yield('< html > < body > < ul > ')
for number in range(minimum, maximum + 1):
yield '< li > %d< / li > ' % number
await asyncio.sleep(0.5)
yield('< / ul > < / body > < / html > ')
class App:
def __init__ (self, scope):
self.scope = scope
async def __call__ (self, receive, send):
generator = slow_numbers(1, 10)
response = StreamingResponse(generator, media_type='text/html')
await response(receive, send)
```
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---
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## Requests
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
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Signature: `Request(scope, receive=None)`
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```python
class App:
def __init__ (self, scope):
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)
```
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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.
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If you don't need to access the request body you can instantiate a request
without providing an argument to `receive` .
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#### Method
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The request method is accessed as `request.method` .
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#### URL
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The request URL is accessed as `request.url` .
The property is actually a subclass of `str` , and also exposes all the
components that can be parsed out of the URL.
For example: `request.url.path` , `request.url.port` , `request.url.scheme` .
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#### Headers
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Headers are exposed as an immutable, case-insensitive, multi-dict.
For example: `request.headers['content-type']`
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#### Query Parameters
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Headers are exposed as an immutable multi-dict.
For example: `request.query_params['abc']`
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#### Body
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There are a few different interfaces for returning the body of the request:
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The request body as bytes: `await request.body()`
The request body, parsed as JSON: `await request.json()`
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You can also access the request body as a stream, using the `async for` syntax:
```python
class App:
def __init__ (self, scope):
self.scope = scope
async def __call__ (self, receive, send):
request = Request(self.scope, receive)
body = b''
async for chunk in request.stream():
body += chunk
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response = Response(body, media_type='text/plain')
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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()` and `.json()` will
raise an error.
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---
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## Routing
Starlette includes a `Router` class which is an ASGI application that
dispatches to other ASGI applications.
```python
from starlette import Router, Path, PathPrefix
from myproject import Homepage, StaticFiles
app = Router([
Path('/', app=Homepage, methods=['GET']),
PathPrefix('/static', app=StaticFiles, methods=['GET'])
])
```
Paths can use URI templating style to capture path components.
```python
Path('/users/{username}', app=User, methods=['GET'])
```
Path components are made available in the scope, as `scope["kwargs"]` .
Because each target of the router is an ASGI instance itself, routers
allow for easy composition. For example:
```python
app = Router([
Path('/', app=Homepage, methods=['GET']),
PathPrefix('/users', app=Router([
Path('/', app=Users, methods=['GET', 'POST']),
Path('/{username}', app=User, methods=['GET']),
]))
])
```
The router will respond with "404 Not found" or "406 Method not allowed"
responses for requests which do not match.
---
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## Test Client
The test client allows you to make requests against your ASGI application,
using the `requests` library.
```python
from starlette import HTMLResponse, TestClient
class App:
def __init__ (self, scope):
self.scope = scope
async def __call__ (self, receive, send):
response = HTMLResponse('< html > < body > Hello, world!< / body > < / html > ')
await response(receive, send)
def test_app():
client = TestClient(App)
response = client.get('/')
assert response.status_code == 200
```
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---
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## Decorators
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The `asgi_application` decorator takes a request/response function and turns
it into an ASGI application.
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The function must take a single `request` argument, and return a response.
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The decorator can be applied to either `async` functions, or to standard
functions.
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```python
from starlette import asgi_application, HTMLResponse
@asgi_application
async def app(request):
return HTMLResponse('< html > < body > Hello, world!< / body > < / html > ')
```
---
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< p align = "center" > < i > Starlette is < a href = "https://github.com/tomchristie/starlette/blob/master/LICENSE.md" > BSD licensed< / a > code.< br / > Designed & built in Brighton, England.< / i > < br / > — ⭐️ — < / p >
