Design question - Sharing of single object by multiple processes

[Steve Holden]

Mike D wrote:
> Hello, I've just picked up the Python language and am really enjoying it.
> 
> I've just signed up to this mailing list and I'm looking forward to 
> taking part in some discussions.
> 
> My first post is a question I've been pondering for the last couple of days:
> 
> For relatively static data (such as a list), is it possible to load a 
> single instance and have many python processes access it?
> 
First there's the problem of having multiple processes access any kind 
of shared resource. So your question makes me wonder whether you mean 
processes, or threads. Are you *sure* you mean processes?

> I want to have an object in memory. This object will be loaded on 
> application start up and will contain a list of objects. These will be 
> obtained from (most likely) the file system.
> 
So "application startup" is different from "process startup"? Your 
application is a group of co-operating processes? Really?

> My reasoning is: I want to prevent a file system or database fetch each 
> time as it seems unnecessary.
> 
It might also seem unnecessary to start the Python interpreter for each 
process, but you are going to have to ...

> Is this possible? In Java I'm pretty sure this could implemented with an 
> object factory and static methods. My understanding is that python 
> invokes a separate process for each request however.
> 
Your understanding is clearly informed by some information you have 
omitted to share with us.

> If possible, what would be a good way of providing a new structure as it 
> is updated.
> 
> If anyone could give me some advice or point me in the correct direction 
> I'd really appreciate it.
> 
> Thanks in advance,
> 
More answers, please. There are mechanisms such as Pyro (Python remote 
objects) that allow inter-process method calls, but I am far from 
convinced that's what you really want (or need, anyway). Perhaps yo 
could let us know a little more about what it really is you are trying 
to do, and convince me, at least, that this isn't just a case of 
premature optimization.

regards
  Steve
-- 
Steve Holden        +1 571 484 6266   +1 800 494 3119
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