python bottle 簡介

本文轉載自查看原文 2017-01-19 14:14 17840 python/ web/ python2.7

　　 bottle 是一個輕量級的python web框架，可以適配各種 web服務器，包括python自帶的wsgiref（默認），gevent， cherrypy，gunicorn等等。bottle是單文件形式發布，源碼在這里可以下載，代碼量不多，可以用來學習web框架。這里也有官方文檔的中文翻譯。

　　首先我們來運行一下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)

　　上面的代碼看起來也非常符合wsgi的接口規范。啟動改代碼，可以看到輸出

Bottle v0.13-dev server starting up (using WSGIRefServer())...

Listening on http://localhost:8080/

Hit Ctrl-C to quit.

　　輸出中加粗部分表明使用的web服務器是 python自帶的wsgiref。也可以使用其他web server，比如gevent，前提是需要安裝gevent，修改后的代碼如下：

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')

通過server關鍵字指定web服務器為‘gevent’，輸出的第一行變成了：

Bottle v0.13-dev server starting up (using GeventServer())...

不管bottle用什么web服務器啟動，在瀏覽器輸入127.0.0.1:8080，都可以看到

下面介紹bottle中部分類和接口

bottle.Bottle

代表一個獨立的wsgi應用，由一下部分組成：routes, callbacks, plugins, resources and configuration。

__call__: Bottle定義了__call__函數, 使得Bottle的實例能成為一個 callable。在前文提到，web框架（或Application）需要提供一個callbale對象給web服務器，bottle提供的就是Bottle實例

    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函數的核心代碼，主要調用兩個比較重要的函數：_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：處理請求，最終調用到application ，簡化后的代碼如下：

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:

　　標准的wsgi接口對Application的返回值要求嚴格，必須迭代返回字符串。bottle做了一些擴展，可以允許App返回更加豐富的類型，比如dict，File等。 _cast函數對_handle函數返回值進行處理，使之符合wsgi規范

bottle.Route

封裝了路由規則與對應的回調

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適配的web服務器的基類，子類只要實現run方法就可以了，bottle里面有大量的Web服務器的適配。下表來自官網，介紹了bottle支持的各種web服務器，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