Python Django Global Variables

Why one mustn't declare global variables? O_o. It just looks like a propaganda. If the author knows what he wants and what side-effects will be, why not. Maybe it's just a quick experiment.

You could declare your counter as a model class-member. Then to deal with race condition you have to add a method that will wait if some other client, from another thread works with counter. Something like this:

import threading

class MyModel(ModelBase):
    _counter = 0
    _counter_lock = threading.Lock()

    @classmethod
    def increment_counter(cls):
        with cls._counter_lock:
            cls._counter += 1

    def some_action(self):
        # core code
        self.increment_counter()


# somewhere else
print MyModel._counter

Remember however: you have to have your application in one process. So if you've deployed the application under Apache, be sure it is configured to spawn many threads, but not many processes. If you're experimenting with ./manage.py run no actions are required.

You mustn't declare global variables. Settings (constants) are OK if done right. But variables violate with shared-nothing architecture and might cause a lot of trouble. (best case they'll be inconsistent)

I would simply store those statistics in the cache. (Well, actually I would store them in the database but you made clear you believe it will have a negative impact on performance, so...)

The new incr() and decr() methods are especially suitable for counting. See docs for more info.

I would create a "config.py" file on the root directory. and put all global variables inside:

x = 10
my_string = ''

at "view.py":

from your_project import config

def MyClass(reuqest):
    y = config.x + 20
    my_title = config.my_string
...

The benefit of creating this file is the variables can cross multiple .py files and it is easy to manage.