You must have observed, all this while we have written tornado based applications that listen on port 8888, and in MySQL post, we had predefined our database connection details (like server, username, password etc). But what if we need to change these details based on modules or applications or configurations? Tornado, provides this with a module tornado.options.
You could use this module in different ways for different purposes.. Lets see them in detail
Example 1:
This is a basic example where the current module define its options with define() method. For instance, port is defined as define(“port”, default=8888)
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| from tornado.options import define, options | |
| import tornado.web | |
| import tornado.database | |
| define("host", default="localhost", help="DB host") | |
| define("database", default="mydb", help="DB used") | |
| define("user", default="root", help="DB username") | |
| define("password", default="root", help="DB Password") | |
| define("port", default=8888) | |
| class DBHandler(tornado.web.RequestHandler): | |
| def get(self): | |
| db = tornado.database.Connection(options.host, options.database, options.user, options.password) | |
| db.close() | |
| application = tornado.web.Application([ | |
| (r"/db", DBHandler), | |
| ], debug=True) | |
| if __name__ == '__main__': | |
| application.listen(options.port) | |
| tornado.ioloop.IOLoop.instance().start() |
Example 2:
It’s always not good to define options for every module separately. Case for some re-usability? Yes, one could define options in a module which can be imported. In this example, all options are defined in opts.py that is imported in the main program.
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| from tornado.options import options,define | |
| define("host", default="localhost", help="DB host") | |
| define("database", default="mydb", help="DB used") | |
| define("user", default="root", help="DB username") | |
| define("password", default="root", help="DB Password") | |
| define("port", default=8888) |
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| from tornado.options import define, options | |
| import tornado.web | |
| import tornado.database | |
| import opts | |
| class DBHandler(tornado.web.RequestHandler): | |
| def get(self): | |
| db = tornado.database.Connection(options.host, options.database, options.user, options.password) | |
| db.close() | |
| application = tornado.web.Application([ | |
| (r"/db", DBHandler), | |
| ], debug=True) | |
| if __name__ == '__main__': | |
| application.listen(options.port) | |
| tornado.ioloop.IOLoop.instance().start() |
Example 3:
Options can also be defined on command line which is possible via tornado.options.parse_command_line(). In the example below, we pass logging level (info|debug|…) on command line, that the module understands with parse_command_line() method.
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| from tornado.options import define, options | |
| import tornado.web | |
| import tornado.database | |
| define("port", default="8888") | |
| class DBHandler(tornado.web.RequestHandler): | |
| def get(self): | |
| self.write("Main") | |
| application = tornado.web.Application([ | |
| (r"/db", DBHandler), | |
| ], debug=True) | |
| if __name__ == '__main__': | |
| tornado.options.parse_command_line() | |
| application.listen(options.port) | |
| tornado.ioloop.IOLoop.instance().start() |
Example 4:
Options can also be defined in a config file with tornado.options.parse_config_file(). In this example, we use config.py to define port, host, database with username and password. We also define port in the main program. But the options for port defined in config py takes precedence and GET on http://localhost:8000/db would work but not on port 8888
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| port="8000" | |
| host="localhost" | |
| databse="mydb" | |
| user="root" | |
| password="root" |
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| from tornado.options import define, options | |
| import tornado.web | |
| import tornado.database | |
| define("port", default="8888") | |
| class DBHandler(tornado.web.RequestHandler): | |
| def get(self): | |
| self.write("Main") | |
| application = tornado.web.Application([ | |
| (r"/db", DBHandler), | |
| ], debug=True) | |
| if __name__ == '__main__': | |
| tornado.options.parse_config_file("config.py") | |
| application.listen(options.port) | |
| tornado.ioloop.IOLoop.instance().start() |
Do you have an idea how we can log errors to seperate file, say for example, error.log in Tornadoweb.
With Tornado options module, you can set the log level with –logging=info or debug or warning on the command line..
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