On 08/09/2017 07:54 AM, Steve D'Aprano wrote:
On Wed, 9 Aug 2017 10:08 am, Ian Pilcher wrote:

I have created a class to provide a "hash consing"[1] set.

Your footnote for [1] appears to be missing. What's a hash consing set? It
appears to be nothing more than frozen sets which you put in a cache so as to
confuse identity and value *wink*

Uugh.  Here's the link:


I doubt very much you're actually saving any time, since you create a temporary
frozen set before returning the one in the cache. You might save some memory

Indeed.  This is all about using memory efficiently.

Your __init__ method does nothing. Get rid of it and save two lines of code :-)

Well, it prevents frozenset.__init__ from being called.

Also, there is at least theoretically the vague possibility that
frozenset.__init__ does something (phones home to Guido?) so you shouldn't
block it if you don't need to.

I do want to prevent frozenset.__init__ from being called *again* when
an existing instance is returned, so I've decided to take this

    def __new__(cls, *args, **kwargs):
        self = super(UniqueSet, cls).__new__(cls, *args, **kwargs)
        self._initialized = False
        return UniqueSet._registry.setdefault(self, self)

    def __init__(self, *args, **kwargs):
        if not self._initialized:
            super(UniqueSet, self).__init__(self, *args, **kwargs)
            self._initialized = True

Ian Pilcher                                         arequip...@gmail.com
-------- "I grew up before Mark Zuckerberg invented friendship" --------


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