I was reading the source code of the Werkzeug library in github and in one of the examples (Simplewiki to name it), in the application.py file there is function which binds the application to the current active context. I would like to know why this is necessary, or where can I find something that explains this?
The function is this:
def bind_to_context(self):
"""
Useful for the shell. Binds the application to the current active
context. It's automatically called by the shell command.
"""
local.application = self
And this is the part where the dispatcher binds the request.
def dispatch_request(self, environ, start_response):
"""Dispatch an incoming request."""
# set up all the stuff we want to have for this request. That is
# creating a request object, propagating the application to the
# current context and instanciating the database session.
self.bind_to_context()
request = Request(environ)
request.bind_to_context()
As far as I know, contexts in the Werkzeug is about separating environment between different threads. For example, contexts are very common thing in the Flask framework which is built on top of the Werkzeug. You can run Flask application in multi-threaded mode. In such case you'll have only one application object which is accessed by multiple threads simultaneously. Each thread requires a piece of data within the app for private usage. Storing such data is organized via thread's local storage. And this is called the context.