[Tutor] Question about the memory manager

[Peter Otten]

Albert-Jan Roskam wrote:

> Hi,
> 
> I just found a neat trick to free up an emergency stash of memory in a
> funtion that overrides sys.excepthook. The rationale is that all
> exceptions, including MemoryErrors will be logged. The code is below. My
> question: is that memory *guaranteed* to be freed right after the 'del'
> statement? Or should one call gc.collect to be really sure?
> 
> rainydayfund = [[] for x in xrange(16*1024)] # or however much you need
> def handle_exception(e):
> global rainydayfund
> del rainydayfund
> ... etc, etc ...
> http://stackoverflow.com/questions/1235349/python-how-can-i-handle-any-unhandled-exception-in-an-alternative-way

I must admit that this looks rather strange to me, but I don't see any 
problem why it wouldn't work. gc.collect() only helps with circular 
dependencies, and there aren't any in your "rainy day fund".

Regarding the use of sys.excepthook I'd rather (SO voting be damned!) take 
the obvious approach as suggested by Vinay Sajip, i. e.

try:
    main()
except:
    # do what you have to do

instead of rewriting the hook. If potential memory resource hogs are 
confined within main() with no references from any module namespace you 
should have enough memory availaible to run the except suite without the 
need for a rainy day fund. If you know about a specific global name that 
references a consumer of a lot of memory, an in-memory db, say, then why not 
handle the memory error there or at least use it in lieu of a dedicated 
dummy? I. e.

in_memory_db = None
try:
    try:
        main()
    finally:
        del in_memory_db
except:
    # do what you have to do