Tornado（5.1+ ）
Hello world
搭建一个简答的web app
hello_world.py
#!/usr/bin/python
# coding=utf-8
"""
tornado demo 1 简单的hello world web app
"""
import sys
import logging
import tornado.ioloop
import tornado.web
class MainHandler(tornado.web.RequestHandler):
def get(self):
self.write("hello world")
url = [(r'/', MainHandler),
]
def app():
global url
return tornado.web.Application(url)
if __name__ == "__main__":
logging.getLogger().handlers = []
logging.basicConfig(stream=sys.stdout, level=logging.DEBUG,
format='%(asctime)s %(levelname)s %(message)s')
ap = app()
ap.listen(9991)
logging.info("starting ....")
tornado.ioloop.IOLoop.current().start()
logging.info("end.")
使用python 启动后，在浏览器访问
python hello_world.py
安装
使用pip源安装
pip install tornado
依赖：
tornado6.0依赖python3.5.2或者更新版本不支持python2（5.1可以支持2.7和3.4+）。
Pycurl : 用来优化tornado.curl_httpclient，libcurl version 7.22或者更高版本
Twisted： may be used with the classes in [**tornado.platform.twisted**](https://www.tornadoweb.org/en/branch5.1/twisted.html#module-tornado.platform.twisted).
pycares： is an alternative non-blocking DNS resolver that can be used when threads are not appropriate.
- monotonic or Monotime ： add support for a monotonic clock, which improves reliability in environments where clock adjustments are frequent. No longer needed in Python 3.
平台： unix-like , 生产环境建议使用Linux（epoll）和BSD（kqueue），发挥最佳性能和伸缩性。window也可以用来开发，官方不建议使用生产。若果不重写IOLoop interface，可能无法添加原声的tornado windows OPLoop实现或者无法发挥windows的IOCP在类似asyncIO或者twisted框架中。
线程和WSGI
tornado不同于其他的很多python web 框架，他不基于WSGI，并且典型的是他只会在每个进程启动一个线程。感兴趣的可以查看更多的异步编程的方法。
While some support of WSGI is available in the [tornado.wsgi](https://www.tornadoweb.org/en/branch5.1/wsgi.html#module-tornado.wsgi) module, it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as [tornado.web](https://www.tornadoweb.org/en/branch5.1/web.html#module-tornado.web)) directly instead of using WSGI.
通常，tornado的code不是线程安全的。唯一的安全方方法是从其他的线程中调用IOLop.add_callback。（In general, Tornado code is not thread-safe. The only method in Tornado that is safe to call from other threads is [IOLoop.add_callback](https://www.tornadoweb.org/en/branch5.1/ioloop.html#tornado.ioloop.IOLoop.add_callback). You can also use [IOLoop.run_in_executor](https://www.tornadoweb.org/en/branch5.1/ioloop.html#tornado.ioloop.IOLoop.run_in_executor) to asynchronously run a blocking function on another thread, but note that the function passed to run_in_executor should avoid referencing any Tornado objects. run_in_executor is the recommended way to interact with blocking code.）
异步io集成
tornado集成了标准库asyncio模块，并且共享了相同的event loop（since 5.0 版本）。所以基于asncio设计的库都可以和tornado自由融合使用。
学习文档
Documentation
This documentation is also available in PDF and Epub formats.
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