CODEWITHSUNDEEP
pythonpython-3.xinitializationtornado
Yuval F
Yuval F

Reputation: 20621

Initialize object once in Tornado web server

I am building a web server using Tornado 4.5.1 and Python 3.6. I want to initialize an object when starting the server and keep it available for the duration of the server run.

From this question: Does initialize in tornado.web.RequestHandler get called every time for a request? I understood that the initialize() functions inside RequestHandlers are called every time there is an HTTP request, and that to initialize once, I need to store this object inside the tornado.web.Application.

My question is: How I add this object to Application initialization? Do I need to subclass tornado.web.Application? Or is there API enabling this?
I couldn't understand this from the Tornado documentation.

Upvotes: 1

Views: 1261

Answers (2)

A. Jesse Jiryu Davis
A. Jesse Jiryu Davis

Reputation: 24007

You can simply make it a module global:

my_global_var = set()  # Or whatever type of object you need

Then the variable will be initialized when your program starts, and last for the program's lifetime. This is the simplest and clearest way to do one-time initialization in Python.

Upvotes: 2

Vitalie Maldur
Vitalie Maldur

Reputation: 591

You can subclass the Application class and after that in your request handler you can access your application instance like this:

RequestHandler.application

or if you are in method from your request handler

self.application

Let's suppose that you have added a variable my_var on your application, to access it you will do:

self.application.my_var

or 

RequestHandler.application.my_var

Upvotes: 2

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