On 10/7/2010 2:39 PM, kj wrote:
Following a suggestion from MRAB, I attempted to implement a
frozendict class.
That really should be built into the language. "dict" is the
last built-in type that doesn't have an immutable form.
John Nagle
--
http://mail.pyth
kj wrote:
> In <878w29kxjp@gmail.com> Arnaud Delobelle writes:
>
> >E.g., try with {1:'a', 1j:'b'}
>
> I see. Thanks for this clarification. I learned a lot from it.
>
> I guess that frozenset must have some way of canonicalizing the
> order of its elements that is dependent on their Pytho
On Fri, 08 Oct 2010 14:00:17 +, kj wrote:
> In kj writes:
>
>>At any rate, using your [i.e. Arnaud's] suggestions in this and your
>>other post, the current implementation of frozendict stands at:
>
>>class frozendict(dict):
>>for method in ('__delitem__ __setitem__ clear pop popitem'
On Fri, 08 Oct 2010 12:10:50 +, kj wrote:
> In <4cae667c$0$29993$c3e8da3$54964...@news.astraweb.com> Steven D'Aprano
> writes:
>
>>On Fri, 08 Oct 2010 00:23:30 +, kj wrote:
>
>>Because it's always better to use a well-written, fast, efficient,
>>correct, well-tested wheel than to invent
In "Jonas H."
writes:
>Hope this helps :-)
It did! Thanks! For one thing now I see that I was barking up
the wrong tree in focusing on a canonical order, when, as the code
you posted shows, it is actually not required for hashing.
In fact, I'd come to the conclusion that frozensets had a c
In "Jonas H."
writes:
>On 10/08/2010 02:23 AM, kj wrote:
>Here's my implementation suggestion:
>class frozendict(dict):
> def _immutable_error(self, *args, **kwargs):
> raise TypeError("%r object is immutable" % self.__class__.__name__)
> __setitem__ = __delitem__ = clear = p
In kj writes:
>At any rate, using your [i.e. Arnaud's] suggestions in this and
>your other post, the current implementation of frozendict stands
>at:
>class frozendict(dict):
>for method in ('__delitem__ __setitem__ clear pop popitem setdefault '
> 'update').split():
>
On 10/08/2010 03:27 PM, kj wrote:
I tried to understand this by looking at the C source but I gave
up after 10 fruitless minutes. (This has been invariably the
outcome of all my attempts at finding my way through the Python C
source.)
It's not you. CPython's code is ... [censored]
Anyway, you
In <878w29kxjp@gmail.com> Arnaud Delobelle writes:
>E.g., try with {1:'a', 1j:'b'}
I see. Thanks for this clarification. I learned a lot from it.
I guess that frozenset must have some way of canonicalizing the
order of its elements that is dependent on their Python values but
not on their
In <4cae667c$0$29993$c3e8da3$54964...@news.astraweb.com> Steven D'Aprano
writes:
>On Fri, 08 Oct 2010 00:23:30 +, kj wrote:
>Because it's always better to use a well-written, fast, efficient,
>correct, well-tested wheel than to invent your own slow, incorrect
>wheel :)
IOW, "don't you wo
On 10/08/2010 02:23 AM, kj wrote:
I imagine that frozenset is better than sorted(tuple(...)) here,
but it's not obvious to me why.
dicts are unsorted. That means their item-order is undefined. So are sets.
If you want a hash that is independent from the order of items, you
could ensure the it
kj writes:
> In <87hbgxlk67@gmail.com> Arnaud Delobelle writes:
>
>>A simple fix is to use hash(frozenset(self.items())) instead.
>
> Thanks for pointing out the hash bug. It was an oversight: I meant
> to write
>
> def __hash__(self):
> return hash(sorted(tuple(self.items(
On Fri, 08 Oct 2010 00:23:30 +, kj wrote:
> In <87hbgxlk67@gmail.com> Arnaud Delobelle
> writes:
>
>>A simple fix is to use hash(frozenset(self.items())) instead.
>
> Thanks for pointing out the hash bug. It was an oversight: I meant to
> write
>
> def __hash__(self):
> re
In <87hbgxlk67@gmail.com> Arnaud Delobelle writes:
>A simple fix is to use hash(frozenset(self.items())) instead.
Thanks for pointing out the hash bug. It was an oversight: I meant
to write
def __hash__(self):
return hash(sorted(tuple(self.items(
I imagine that frozenset i
Oops I sent off my reply before I had finished!
kj writes:
> Following a suggestion from MRAB, I attempted to implement a
> frozendict class. My implementation took a lot more work than
> something this simple should take, and it still sucks. So I'm
> hoping someone can show me a better way.
kj writes:
> Following a suggestion from MRAB, I attempted to implement a
> frozendict class. My implementation took a lot more work than
> something this simple should take, and it still sucks. So I'm
> hoping someone can show me a better way. Specifically, I'm hoping
> that there is a "recip
Following a suggestion from MRAB, I attempted to implement a
frozendict class. My implementation took a lot more work than
something this simple should take, and it still sucks. So I'm
hoping someone can show me a better way. Specifically, I'm hoping
tha
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