Also, note that your 'results' dict will only persist for the duration of a single request. Each request is handled by a new thread (from a thread pool).
Anthony On Saturday, September 17, 2011 11:06:14 AM UTC-4, Massimo Di Pierro wrote: > > On Sep 17, 6:31 am, Chris Rowson <christop...@gmail.com> wrote: > > Hi folks, > > > > I'm trying to get my head around what happens to data stored in memory > when > > it isn't needed anymore. > > > > Let me give you an example. Let's say I create a function which returns a > > > dict called 'results' populated with data from an external source each > time > > a user registers (for instance let's say it has data returned from > geocoding > > the users postcode and providing info about the area). > > > > So the 'results' dict holds that data, it is used, and then what? Is the > > memory automatically freed up again when we finish with the data or does > it > > hang around in memory? > > Yes. Python uses reference counting. Every variable is a pointer to a > memory location. It keeps tracks of how many pointers point to the > same location. > > a = A() # one pointer > b = a # two pointers > c = a # three pointers > > when you delete one the counter is decreased > > b = 4 # now two variables (a,c) point to A() > > when the counter is zero the object is freed. > > This works great UNLESS the objects have circular references (a.x=a) > AND the object has a destructor (A.__del__). As long a you do not use > destructors (who needs them?) everything works great. > > > > >
