[Python-Dev] chained assignment weirdity

Ned Batchelder ned at nedbatchelder.com
Wed Nov 7 22:39:28 CET 2012

On 11/7/2012 12:08 PM, Serhiy Storchaka wrote:
> On 07.11.12 17:12, Nick Coghlan wrote:
>> Since you've indicated the implementation is in the wrong here and you
>> also want to preserve opcode semantics, I think Skip's patch is
>> correct, but also needs to be applied to dict comprehensions (now we
>> have them). The extra bytecode is only ROT_TWO, which is one of the
>> cheapest we have kicking around :)
> Not only to dict comprehensions, but also to item assignments.  It 
> will be weird if a dict comprehension and a plain loop will be 
> inconsistent.
Just to be clear: the reference guide says that the behavior *SHOULD BE* 
(but is not yet) this:

    Python 3.3.0
     >>> {print("a"):print("b")}
    {None: None}
     >>> d = {}
     >>> d[print("a")] = print("b")

Is this or is this not "weird" to you?


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