bottle 是一个轻量级的python web框架, 可以适配各种web服务器,包括python自带的wsgiref(默认),gevent, cherrypy,gunicorn等等。bottle是单文件形式发布,源码在这里可以下载,代码量不多,可以用来学习web框架。这里也有官方文档的中文翻译。
首先我们来运行一下bottle的hello world
from bottle import run if __name__ == '__main__': def application(environ, start_response): start_response('200 OK', [('Content-Type', 'text/html')]) return ['<h1>Hello world!</h1>'] run(host='localhost', port=8080, app=application)
上面的代码看起来也非常符合wsgi的接口规范。启动改代码,可以看到输出
Bottle v0.13-dev server starting up (using WSGIRefServer())...
Listening on http://localhost:8080/
Hit Ctrl-C to quit.
输出中加粗部分表明使用的web服务器是python自带的wsgiref。也可以使用其他web server,比如gevent,前提是需要安装gevent,修改后的代码如下:
from bottle import run import gevent.monkey gevent.monkey.patch_all() if __name__ == '__main__': def application(environ, start_response): start_response('200 OK', [('Content-Type', 'text/html')]) return ['<h1>Hello world!</h1>'] run(host='localhost', port=8080, app=application, server = 'gevent')
通过server关键字指定web服务器为‘gevent’,输出的第一行变成了:
Bottle v0.13-dev server starting up (using GeventServer())...
不管bottle用什么web服务器启动,在浏览器输入127.0.0.1:8080,都可以看到
![](https://images2015.cnblogs.com/blog/1089769/201701/1089769-20170118143653406-2015123281.png)
下面介绍bottle中部分类和接口
bottle.Bottle
代表一个独立的wsgi应用,由一下部分组成:routes, callbacks, plugins, resources and configuration。
__call__: Bottle定义了__call__函数, 使得Bottle的实例能成为一个callable。在前文提到,web框架(或Application)需要提供一个callbale对象给web服务器,bottle提供的就是Bottle实例
def __call__(self, environ, start_response): """ Each instance of :class:'Bottle' is a WSGI application. """ return self.wsgi(environ, start_response)
下面是Bottle.wsgi函数的核心代码,主要调用两个比较重要的函数:_handle, _cast
def wsgi(self, environ, start_response): """ The bottle WSGI-interface. """ try: out = self._cast(self._handle(environ)) # rfc2616 section 4.3 if response._status_code in (100, 101, 204, 304)\ or environ['REQUEST_METHOD'] == 'HEAD': if hasattr(out, 'close'): out.close() out = [] start_response(response._status_line, response.headerlist) return out
_handle:处理请求,最终调用到application ,简化后的代码如下:
1 def _handle(self, environ): 2 self.trigger_hook('before_request') 3 route, args = self.router.match(environ) 4 out = route.call(**args) 5 self.trigger_hook('after_request') 6 return out
_cast:
标准的wsgi接口对Application的返回值要求严格,必须迭代返回字符串。bottle做了一些扩展,可以允许App返回更加丰富的类型,比如dict,File等。 _cast函数对_handle函数返回值进行处理,使之符合wsgi规范
bottle.Route
封装了路由规则与对应的回调
bottle.Router
A Router is an ordered collection of route->target pairs. It is used to efficiently match WSGI requests against a number of routes and return the first target that satisfies the request.
ServerAdapter
所有bottle适配的web服务器的基类,子类只要实现run方法就可以了,bottle里面有大量的Web服务器的适配。下表来自官网,介绍了bottle支持的各种web服务器,以及各自的特性。
Name | Homepage | Description |
---|---|---|
cgi | Run as CGI script | |
flup | flup | Run as FastCGI process |
gae | gae | Helper for Google App Engine deployments |
wsgiref | wsgiref | Single-threaded default server |
cherrypy | cherrypy | Multi-threaded and very stable |
paste | paste | Multi-threaded, stable, tried and tested |
rocket | rocket | Multi-threaded |
waitress | waitress | Multi-threaded, poweres Pyramid |
gunicorn | gunicorn | Pre-forked, partly written in C |
eventlet | eventlet | Asynchronous framework with WSGI support. |
gevent | gevent | Asynchronous (greenlets) |
diesel | diesel | Asynchronous (greenlets) |
fapws3 | fapws3 | Asynchronous (network side only), written in C |
tornado | tornado | Asynchronous, powers some parts of Facebook |
twisted | twisted | Asynchronous, well tested but... twisted |
meinheld | meinheld | Asynchronous, partly written in C |
bjoern | bjoern | Asynchronous, very fast and written in C |
auto | Automatically selects an available server adapter |
可以看到,bottle适配的web服务器很丰富。工作模式也很全面,有多线程的(如paste)、有多进程模式的(如gunicorn)、也有基于协程的(如gevent)。具体选择哪种web服务器取决于应用的特性,比如是CPU bound还是IO bound
bottle.run
启动wsgi服务器。几个比较重要的参数
app: wsgi application,即可以是bottle.Bottle 也开始是任何满足wsgi 接口的函数
server: wsgi http server,字符串
host:port: 监听端口
核心逻辑:
ServerAdapter.run(app)。
最后,bottle源码中有一些使用descriptor的例子,实现很巧妙,值得一读,前文也有介绍。
references;