[Python-Dev] A new dictionary implementation (original) (raw)

Yury Selivanov yselivanov.ml at gmail.com
Wed Feb 15 22:09:17 CET 2012

Hello Mark,

First, I've back-ported your patch on python 3.2.2 (which was relatively easy). Almost all tests pass, and those that don't are always failing on my machine if I remember. The patch can be found here: http://goo.gl/nSzzY

Then, I compared memory footprint of one of our applications (300,000 LOC) and saw it about 6% less than on vanilla python 3.2.2 (660 MB of reserved process memory compared to 702 MB; Linux Gentoo 64bit) The application is written in heavy OOP style (for instance, ~1000 classes are generated by our ORM on the fly, and there are approximately the same amount of hand-written ones) so I hoped for a much bigger saving.

As for the patch itself I found one use-case, where python with the patch behaves differently::

class Foo: def init(self, msg): self.msg = msg

f = Foo('123')

class _str(str): pass

print(f.msg) print(getattr(f, _str('msg')))

The above snippet works perfectly on vanilla py3.2, but fails on the patched one (even on 3.3 compiled from your 'cpython_new_dict' branch) I'm not sure that it's a valid code, though. If not, then we need to fix some python internals to add exact type check in 'getattr', in the 'operator.getattr', etc.
And if it is - your patch needs to be fixed. In any case, I propose to add the above code to the python test-suite, with either expecting a result or an exception.

Cheers, Yury

On 2012-02-15, at 12:58 PM, Mark Shannon wrote:

Any opinions on my new dictionary implementation?

I'm happy to take silence on the PEP as tacit approval, but the code definitely needs reviewing. Issue: http://bugs.python.org/issue13903 PEP: https://bitbucket.org/markshannon/cpythonnewdict/src/6c4d5d9dfc6d/pep-new-dict.txt Repository https://bitbucket.org/markshannon/cpythonnewdict Cheers, Mark.

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