Mark T wrote:
>
> "Alex Martelli" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
>
>> John Nagle <[EMAIL PROTECTED]> wrote:
>>
>>> Marcin Ciura wrote:
>>>
>>> > Neither would I. I must have expressed myself not clearly enough.
>>> > Currently
>>> > x = y = z
>>> > is roughly equivalent to
>>> > x = z
>>> > y = z
>>> > I propose to change it to
>>> > y = z
>>> > x = z
>>>
>>> Actually, it is equivalent to
>>>
>>> y = z
>>> x = y
>>
>>
>> Not really:
>>
>>>>> class chatty(object):
>>
>> ... def __init__(self): self.__dict__['__hide'] = {}
>> ... def __setattr__(self, name, value):
>> ... print 'sa', name, value
>> ... self.__dict__['__hide'][name] = value
>> ... def __getattr__(self, name):
>> ... print 'ga', name
>> ... return self.__dict__['__hide'].get(name)
>> ...
>>
>>>>> c = chatty()
>>>>> x = c.zop = 23
>>
>> sa zop 23
>>
>>>>>
>>
>> As you can see, there is no read-access to c.zop, which plays the role
>> of y there.
>>
>>
>> Alex
>
>
> This is interesting:
>
>>>> class Test(object):
>
> ... def __getattribute__(self,n):
> ... print 'reading',n
> ... return object.__getattribute__(self,n)
> ... def __setattr__(self,n,v):
> ... print 'writing',n,v
> ... return object.__setattr__(self,n,v)
> ...
>
>>>> x=Test()
>>>> x.a=1; x.b=2; x.c=3
>
> writing a 1
> writing b 2
> writing c 3
>
>>>> x.a=x.b=x.c
>
> reading c
> writing a 3
> writing b 3
>
>>>>
>
> I wouldn't have expected "a" to be assigned first in a right-to-left
> parsing order. The result is the same in any case.
>
> -Mark T.
That's fascinating. Is that a documented feature of the language,
or a quirk of the CPython interpreter?
John Nagle
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