How to free memory ( ie garbage collect) at run time with Python 2.5.1(windows)

[Alex Martelli]

rfv-370 <robert.vergnes at yahoo.fr> wrote:

> have made the following small test:
> 
> Before starting my test my UsedPhysicalMemory(PF): 555Mb
> 
> >>>tf=range(0,10000000)    PF: 710Mb ( so 155Mb for my List)
> >>>tf=[0,1,2,3,4,5]             PF: 672Mb (Why? Why the remaining 117Mb is
> >>>not freed?) del tf                            PF: 672Mb (unused memory
> >>>not freed)

Integer objects that are once generated are kept around in a "free list"
against the probability that they might be needed again in the future (a
few other types of objects similarly keep a per-type free-list, but I
think int is the only one that keeps an unbounded amount of memory
there).  Like any other kind of "cache", this free-list (in normal
cases) hoards a bit more memory than needed, but results in better
runtime performance; anomalous cases like your example can however
easily "bust" this too-simple heuristic.

> So how can I force Python to clean the memory and free the memory that
> is not used?

On Windows, with Python 2.5, I don't know of a good approach (on Linux
and other Unix-like systems I've used a strategy based on forking, doing
the bit that needs a bazillion ints in the child process, ending the
child process; but that wouldn't work on Win -- no fork).

I suggest you enter a feature request to let gc grow a way to ask every
type object to prune its cache, on explicit request from the Python
program; this will not solve the problem in Python 2.5, but work on 3.0
is underway and this is just the right time for such requests.


Alex