Is it possible to get the Physical memory address of a variable in python?

[Maxim Khitrov]

On Tue, Nov 10, 2009 at 6:32 AM, Ognjen Bezanov <Ognjen at mailshack.com> wrote:
> Hey,
>
> Thanks for all the responses guys. In hindsight I probably should have
> explained why on earth I'd need the physical address from an interpreted
> language.
>
> I'm trying to see if there is any way I can make Python share data between
> two hosts using DMA transfers over a firewire connection, so avoiding the
> need for another layer on top such as IPv4 + Python sockets.
>
> Thanks to some old python bindings which I updated to python 2.6, I can read
> any write to the RAM of any firewire connected host within python. Because
> it uses DMA (the cpu is not involved in this at all), I can only specify a
> physical address within the 4GB ram limit to read from and write to.
>
> Now what I've done so far is on the remote host I run python and set a
> variable as so:
>
> a = "foo"
> print a
> 'foo'
>
> Then on the local host I run a python script that scans the entire RAM
> looking for the string "foo", and replaces it with the string "oof". I have
> had success with this method. Once it's done and I do "print a" on the
> remote host, I get "oof" as the variable value, so in theory it can work.
>
> Problem is that it's slow. Scanning 3GB of RAM every time you want to do
> this is not a good method. I thought that if I could get python to return
> the physical address of where the value of a variable is, then I can just
> jump to that address and write the data.
>
> From what I've been told so far, it's not possible to do this without some
> OS-specific (Linux in this case) syscall. Is this correct?
>
> Thanks!
>
>
> Ognjen

If all you need is a memory buffer, array.array provides a
buffer_info() method that tells you the current (virtual) address. For
DMA, I think there are dma_map_* functions in linux that you may be
able to call through ctypes.

- Max