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[Python-Dev] PEP 0424: A method for exposing a length hint

Ethan Furman ethan at stoneleaf.us
Mon Jul 16 21:59:20 CEST 2012 
M Stefan wrote:
> Also, what would iter([1,2,3]).__length_hint__() return? 3 or unknown?
> If 3, then the semantics of l=[1,2,3]; l += iter(l) will change 
> (infinite loop without __length_hint__ vs. list of 6 elements with __length_hint__).

What __length_hint__ returns is irrelevant -- it's only a hint.  Python 
will have to loop over all the items.  So you would still get an 
infinite loop with the above code.

~Ethan~
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