pdb调试

n 运行下一行代码
p 计算p后面的表达式(当前上下文中), 并打印表达式的值
s 进入函数
r 从函数中返回
b 动态设置断点
w 打印当前栈信息
q 退出pdb

Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. By using non-blocking network I/O, Tornado can scale to tens of thousands of open connections, making it ideal for long polling, WebSockets, and other applications that require a long-lived connection to each user.