python bottle 简介

Posted 2020-09-18

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　　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

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