Tornado web简介

Thread-safety notes：

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In general, methods on RequestHandler and elsewhere in tornado are not thread-safe. In particular, methods such as write(), finish(), and flush() must only be called from the main thread. If you use multiple threads it is important to use IOLoop.add_callback to transfer control back to the main thread before finishing the request.

Collections:

• 1、functools.partial用法
• 2、tornado.web.asynchronous用法

引用

functools.partial(func[,*args][, **keywords])Return a new partial object which when called will behave like func called with the positional arguments args and keyword arguments keywords. If more arguments are supplied to the call, they are appended to args. If additional keyword arguments are supplied, they extend and override keywords.

For example, partial() can be used to create a callable that behaves like the int() function where the base argument defaults to two

>>> import functors
>>> f=functools.partial(int, base=2)
>>> f.args
()
>>> f.func
<type 'int'>
>>> f.keywords
{'base': 2}

>>>from functools imports partial
>>>basetwo = partial(int, base=2)
>>>basetwo('10010')
18

一般，函数在执行时，需要带上所必要的参数进行调用。然后，有时参数可以在函数被调用前提前获知。这种情况下，一个函数有一个或多个参数预先就能用上，一遍函数能用更少的参数进行调用。

Decorators:

tornado.web.asynchronous(method)
Wrap request handler methods with this if they are asynchronous.

引用

If this decorator is given, the response is not finished when the method returns. It is up to the request handler to call self.finish() to finish the HTTP request. Without this decorator, the request is automatically finished when the get() or post() method returns.

class MyRequestHandler(web.RequestHandler):
    @web.asynchronous
    def get(self):
       http = httpclient.AsyncHTTPClient()
       http.fetch("http://friendfeed.com/", self._on_download)
    def _on_download(self, response):
       self.write("Downloaded!")
       self.finish()

示例：

#!/usr/bin/env python
#-*-coding:utf-8-*-
import tornado
import functors
import tornado.httpserver
from tornado.web import RequestHandler
from tornado.httpclient import AsyncHTTPClient

class AsyncHandler(RequestHandler):
    @tornado.web.asynchronous
    def get(self):
        http_client = AsyncHTTPClient()
        http_client.fetch("http://www.google.com",
                          callback=functools.partial(self.on_fetch,'love it'))
        
    def on_fetch(self, param, response):
        print response.body
        print param
        self.write('This is a demo.')
        self.finish()

settings = {
    "debug": True,
}

application = tornado.web.Application([
    (r"/", AsyncHandler),
], **settings)

if __name__ == "__main__":

    http_server = tornado.httpserver.HTTPServer(application)
    http_server.listen(8088)
    tornado.ioloop.IOLoop.instance().start()  

tornado.web.authenticated(method)

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Decorate methods with this to require that the user be logged in.

tornado.web.addslash(method)

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Use this decorator to add a missing trailing slash to the request path.
For example, a request to ‘/foo’ would redirect to ‘/foo/’ with this decorator. Your request handler mapping should use a regular expression like r’/foo/?’ in conjunction with using the decorator.

tornado.web.removeslash(method)

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Use this decorator to remove trailing slashes from the request path.
For example, a request to '/foo/' would redirect to '/foo' with this decorator. Your request handler mapping should use a regular expression like r'/foo/*'in conjunction with using the decorator.

Others:

一、@property可以把function变成属性。

引用

property([fget[,fset[,fdel[,doc]]]])Return a property attribute for new-style classes (classes that derive from object).

If given, doc will be the docstring of the property attribute. Otherwise, the property will copy fget‘s docstring (if it exists). This makes it possible to create read-only properties easily using property() as a decorator:

示例：

class Person(object):

    def __init__(self):

        self._name = ''

    def fget(self):

        print "Getting: %s" % self._name
        return self._name 

    def fset(self, value):

        print "Setting: %s" % value
        self._name = value.title()

    def fdel(self):

        print "Deleting: %s" %self._name
        del self._name

    name = property(fget, fset, fdel, "I'm the property.")

p=Person()
p.name='Eric Su'
p.name
del p.name

引用

A property object has getter, setter, and deleter methods usable as decorators that create a copy of the property with the corresponding accessor function set to the decorated function.

Descriptors:

class Person(object):

    def __init__(self):

        self._name = ''

    @property
    def name(self):

        print "Getting: %s" % self._name
        return self._name

    @name.setter
    def name(self, value):

        print "Setting: %s" % value
        self._name = value.title()

    @name.deleter
    def name(self):

        print "Deleting: %s" % self._name
        del self._name

p=Person()
p.name='Eric Su'
p.name
del p.name

有关另外异步调用tornado.gen以及generator的用法会在下一篇进行整理。参考资料：
http://joy2everyone.iteye.com/blog/910950
http://docs.python.org/2/library/functools.html
http://www.tornadoweb.org/documentation/web.html
http://docs.python.org/2/library/functions.html#property
http://www.ibm.com/developerworks/library/os-pythondescriptors/index.html
http://stackoverflow.com/questions/6618002/python-property-versus-getters-and-setters
http://stackoverflow.com/questions/3252228/python-why-is-functools-partial-necessary