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On 02/14/2015 11:41 AM, Chris Barker wrote:
On Sat, Feb 14, 2015 at 11:12 AM, Ethan Furman wrote:
On 02/13/2015 06:57 PM, Andrew Barnert wrote:
The current design of Python guarantees that an object always gets a setattr or setitem when one of its elements is assigned to. That's an important property, for the reasons I suggested above. So any change would have to preserve that property. And skipping assignment when __iadd__ returns self would not preserve that property. So it's not just backward-incompatible, it's bad.
--> some_var = ([1], 'abc') --> tmp = some_var[0] --> tmp += [2, 3] --> some_var ([1, 2, 3], 'abc')
In that example, 'some_var' is modified without its __setitem__ ever being called.
not really -- an object in the some_var is modified -- there could be any number of other references to that object -- so this is very much how python works.
Oops, I misread what Andrew was saying, sorry! -- ~Ethan~