In <4cb1dc9a$0$29970$c3e8da3$54964...@news.astraweb.com> Steven D'Aprano
writes:
>Reading the source code is also a good approach.
Every time I have attempted to answer a question by looking at the
Python C source, all I've achieved was wasting time, sometimes a
*lot* of time, so by now I've de
Arnaud Delobelle writes:
> I have learnt too that hash(-1) is not (-1), and that it seems that a
> hash value is not allowed to be (-1). There is one thing left to find
> out. Why can't it be (-1)?
Because -1 has a special meaning in the C function equivalent to
Python's hash(). PyObject_Hash
kj writes:
> In <87hbgu8irb@gmail.com> Arnaud Delobelle writes:
[...]
>>And, in fact,
>>(-1) is the only int such that hash(x) != x.
>
> Arnaud, how did you determine that -1 is the only such int? I
> can't imagine any other approach other than a brute-force check of
> all ints... When I
On Sun, 10 Oct 2010 13:49:09 +, kj wrote:
>>> to give only two of an infinite number of counter-examples.
>
> (Infinite???)
I was mistaken. Given Arnaud's specification that we look only at the
Python 2.x ints, I believe that there is only one counter-example, namely
-1.
However, in Pytho
On Sun, 10 Oct 2010 11:06:00 +0100, Arnaud Delobelle wrote:
> Steven D'Aprano writes:
>
>> On Sat, 09 Oct 2010 21:39:51 +0100, Arnaud Delobelle wrote:
>>
>>> 1. hash() is an idempotent function, i.e. hash(hash(x)) == hash(x)
>>> hold for any hashable x (this is a simple consequence of the fact t
In <87hbgu8irb@gmail.com> Arnaud Delobelle writes:
>Steven D'Aprano writes:
>> On Sat, 09 Oct 2010 21:39:51 +0100, Arnaud Delobelle wrote:
>>
>>> 1. hash() is an idempotent function, i.e. hash(hash(x)) == hash(x) hold
>>> for any hashable x (this is a simple consequence of the fact that
>>>
Steven D'Aprano writes:
> On Sat, 09 Oct 2010 21:39:51 +0100, Arnaud Delobelle wrote:
>
>> 1. hash() is an idempotent function, i.e. hash(hash(x)) == hash(x) hold
>> for any hashable x (this is a simple consequence of the fact that
>> hash(x) == x for any int x (by 'int' I mean 2.X int)).
>
> It'
Steven D'Aprano writes:
> On Sat, 09 Oct 2010 21:39:51 +0100, Arnaud Delobelle wrote:
>
>> 1. hash() is an idempotent function, i.e. hash(hash(x)) == hash(x) hold
>> for any hashable x (this is a simple consequence of the fact that
>> hash(x) == x for any int x (by 'int' I mean 2.X int)).
>
> It'
On Sat, 09 Oct 2010 21:39:51 +0100, Arnaud Delobelle wrote:
> 1. hash() is an idempotent function, i.e. hash(hash(x)) == hash(x) hold
> for any hashable x (this is a simple consequence of the fact that
> hash(x) == x for any int x (by 'int' I mean 2.X int)).
It's a beautiful theory, but, alas, it
kj writes:
> In <87y6a9lqnj@gmail.com> Arnaud Delobelle writes:
>
>>You could do something like this:
>
>>deep_methods = {
>>list: lambda f, l: tuple(map(f, l)),
>>dict: lambda f, d: frozenset((k, f(v)) for k, v in d.items()),
>>set: lambda f, s: frozenset(map(f, s)),
>>
In <87y6a9lqnj@gmail.com> Arnaud Delobelle writes:
>You could do something like this:
>deep_methods = {
>list: lambda f, l: tuple(map(f, l)),
>dict: lambda f, d: frozenset((k, f(v)) for k, v in d.items()),
>set: lambda f, s: frozenset(map(f, s)),
># Add more if needed
kj writes:
> The short version of this question is: where can I find the algorithm
> used by the tuple class's __hash__ method?
>
> Now, for the long version of this question, I'm working with some
> complext Python objects that I want to be able to compare for
> equality easily.
>
> These object
On 07/10/2010 11:42, kj wrote:
In Terry
Reedy writes:
If these two attributes, and hence the dicts, are public, then your
instances are mutable.
I guess I should have written "immutable among consenting adults."
As far as I know, Python does not support private attributes, so
I guess the
kj writes:
> In <87pqvmp611@web.de> de...@web.de (Diez B. Roggisch) writes:
>
>>I tried codesearch first. Not satisfied after 30 seconds with the
>>results, I did the most straight forward thing - I downloaded and
>>un-packed the python source... and took a look.
>
>>From that I learned the
In <87pqvmp611@web.de> de...@web.de (Diez B. Roggisch) writes:
>I tried codesearch first. Not satisfied after 30 seconds with the
>results, I did the most straight forward thing - I downloaded and
>un-packed the python source... and took a look.
>From that I learned the tuplehash function na
kj writes:
> In de...@web.de (Diez B. Roggisch) writes:
>
>>kj writes:
>
>>> The short version of this question is: where can I find the algorithm
>>> used by the tuple class's __hash__ method?
>
>>Surprisingly, in the source:
>
>>http://google.com/codesearch/p?hl=de#-2BKs-LW4I0/trunk/python/sr
In de...@web.de (Diez B. Roggisch) writes:
>kj writes:
>> The short version of this question is: where can I find the algorithm
>> used by the tuple class's __hash__ method?
>Surprisingly, in the source:
>http://google.com/codesearch/p?hl=de#-2BKs-LW4I0/trunk/python/src/Objects/tupleobject.c&
In Terry Reedy
writes:
>If these two attributes, and hence the dicts, are public, then your
>instances are mutable.
I guess I should have written "immutable among consenting adults."
As far as I know, Python does not support private attributes, so
I guess the dicts are public no matter what
On 10/6/2010 2:58 PM, kj wrote:
These objects are non-mutable once they are created,
See below.
like to use a two-step comparison for equality, based on the
assumption that I can compute (either at creation time, or as needed
and memoized) a hashkey/digest for each object. The test for
equa
On 10/6/10 1:58 PM, kj wrote:
The short version of this question is: where can I find the algorithm
used by the tuple class's __hash__ method?
The function tuplehash() in Objects/tupleobject.c, predictably enough.
Now, for the long version of this question, I'm working with some
complext Pyt
kj writes:
> The short version of this question is: where can I find the algorithm
> used by the tuple class's __hash__ method?
Surprisingly, in the source:
http://google.com/codesearch/p?hl=de#-2BKs-LW4I0/trunk/python/src/Objects/tupleobject.c&q=python%20tuplehash&sa=N&cd=1&ct=rc
> Now, for t
On Wed, Oct 6, 2010 at 11:58 AM, kj wrote:
>
>
> The short version of this question is: where can I find the algorithm
> used by the tuple class's __hash__ method?
>From Objects/tuple.c, line 315 in Python3.2:
static long
tuplehash(PyTupleObject *v)
{
register long x, y;
register Py_ssiz
kj wrote:
> The short version of this question is: where can I find the algorithm
> used by the tuple class's __hash__ method?
>
http://svn.python.org/view/python/trunk/Objects/tupleobject.c?revision=81029&view=markup
static long
tuplehash(PyTupleObject *v)
{
register long x, y;
regist
The short version of this question is: where can I find the algorithm
used by the tuple class's __hash__ method?
Now, for the long version of this question, I'm working with some
complext Python objects that I want to be able to compare for
equality easily.
These objects are non-mutable once th
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