On 06/06/2013 11:46 AM, Haoyi Li wrote: >>That would make += misleading. In any other language with a += operator, it mutates > > Does it? Which is all irrelevant. Python already has a well-defined meaning for += and friends, which is in-place mutation*. *Immutables, of course, fall back to the corresponding non-mutatation methods. -- ~Ethan~