[Python-Dev] Should the default equality operator compare values instead of identities?

[Ronald Oussoren]

On 7-nov-2005, at 23:34, Martin v. Löwis wrote:

> BJörn Lindqvist wrote:
>> How would the value equality operator deal with recursive objects?
>>
>> class Foo:
>>     def __init__(self):
>>         self.foo = self
>>
>> Seems to me that it would take atleast some special-casing to get
>> Foo() == Foo() to evalute to True in this case...
>
> This is sort-of supported today:

But only for lists ;-)

 >>> a = {}
 >>> a[1] = a
 >>>
 >>> b = {}
 >>> b[1] = b
 >>>
 >>> a == b
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
RuntimeError: maximum recursion depth exceeded in cmp
 >>>

>
>>>> a=[]
>>>> a.append(a)
>>>> b=[]
>>>> b.append(b)
>>>> a == b
> True
>
> Regards,
> Martin
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