[Python-Dev] PEP-0218

Moshe Zadka moshez@zadka.site.co.il
Thu, 30 Nov 2000 16:52:59 +0200

> BTW, one lesson to take from SETL:  a vital set operation in practice is a
> mutating "pick a 'random' element E from the set, remove it from the set,
> and return it".  An enormous number of set algorithms are of the form
>     while not S.empty():
>         pick some element from S
>         deal with it, possibly mutating S
> This operation can't be done efficiently in Python code if the set is
> represented by a dict (the best you can do is materialize the full list of
> keys first, and pick one of those).  That means my Set class often takes
> quadratic time for what *should* be linear-time algorithms.

Hmmm...actually, I've been wanting a method .key() for dictionaries 
a long time. So if we give dictionaries this one small method, then
we *can* do this in Python.

Moshe Zadka <sig@zadka.site.co.il>
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