[Python-ideas] Why does += trigger UnboundLocalError?

Ethan Furman ethan at stoneleaf.us
Thu Jun 2 01:47:19 CEST 2011

Steven D'Aprano wrote:
> Carl M. Johnson wrote:
>> Agreed, sure, we have to treat the LHS of = as
>> a local. But += is fundamentally different. 
> No it's not. It is fundamentally the same. Augmented assignment in 
> Python *is* assignment, equivalent to x = x.__iadd__(other).

Or x = x.__add__(other) if no __iadd__ exists for the object.


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