An async proof of concept for eventual variables.

example_usage.py

def endpoint(request):
        # This will enqueue this database query in the background, if anything
        #  uses request.user later, it will hopefully have finished the query,
        #  otherwise it will block on that query
        request.user = db.later(db.query("SELECT * FROM users WHERE id=?", (
            request.cookies.get("user"), )))

proof_of_concept.py

import time, thread

class EventualVar(object):
    def __init__(self, caller, *args, **kwargs):
        kwargs['result'] = self
        self.caller = caller
        thread.start_new_thread(self.caller, args, kwargs)
        self.value = None

    def __set__(self, instance, value):
        self.value = value

    def __get__(self, instance, owner):
        while not self.value:
            time.sleep(0.01)
        return self.value

class X():
    pass

def data_getter(data, result):
    time.sleep(1)
    result.value = data

def works():
    X.var = EventualVar(data_getter, 5)
    time.sleep(2)
    print X.var

def also_works():
    X.var = EventualVar(data_getter, 5)
    print X.var

for test in [works, also_works]:
    print "Running %s" % test.__name__
    start = time.time()
    test()
    print "Took %s" % (time.time() - start)