[Python-Dev] cpython: Implement PEP 412: Key-sharing dictionaries (closes #13903)

Kristján Valur Jónsson kristjan at ccpgames.com
Wed Apr 25 11:11:51 CEST 2012

> -----Original Message-----
> From: python-dev-bounces+kristjan=ccpgames.com at python.org
> [mailto:python-dev-bounces+kristjan=ccpgames.com at python.org] On
> Behalf Of martin at v.loewis.de
> Sent: 24. apríl 2012 17:44
> To: python-dev at python.org
> Subject: Re: [Python-Dev] cpython: Implement PEP 412: Key-sharing
> dictionaries (closes #13903)
> > Benchmarks should measure memory usage too, of course.  Sadly that is
> > not possible in standard cPython.
> It's actually very easy in standard CPython, using sys.getsizeof.
Yes, you can query each python object about how big it thinks it is.
What I'm speaking of is more like:
start_allocs, start_mem = allocator.get_current()

end_allocs, end_mem = allocator.get=current()

Print "delta blocks: %d, delta mem: %d"%(end_allocs-start_allocs, end_mem-start_mem)
print "peak blocks: %d, peak mem: %d"%allocator.peak()

> > Btw, this is of great interest to me at the moment, our Shanghai
> > engineers are screaming at the memory waste incurred by dictionaries.
> > A 10 item dictionary consumes 1/2k on 32 bits, did you know this?
> I did.
> In Python 3.3, this now goes down to 248 bytes (32 bits).
I'm going to experiment with tunable parameters in 2.7 to trade performance for memory.  In some applications, memory trumps performance.


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