On Sat, 01 May 2010 07:13:42 -0500, Tim Chase wrote: > On 05/01/2010 12:08 AM, Patrick Maupin wrote: >> +=, -=, /=, *=, etc. conceptually (and, if lhs object supports in- >> place operator methods, actually) *modify* the lhs object. >> >> Your proposed .= syntax conceptually *replaces* the lhs object >> (actually, rebinds the lhs symbol to the new object). > > The += family of operators really do rebind the symbol, not modify the > object.
They potentially do both, depending on the object, even for built-ins. > >>> from decimal import Decimal [...] I'm not sure why you took the trouble to import Decimal for this example, when you could have shown the same thing with built-ins int or float. All three types are immutable. A counter example with a mutable type: >>> a = [] >>> b = a >>> a += [2] >>> a [2] >>> b [2] thus demonstrating that __iadd__ modifies in place as well as rebinds for at least one mutable type. > This doesn't preclude you from implementing a self-mutating += style > __add__ method and returning "self", but it's usually a bad idea Obviously the Python dev team don't agree with that :) Just to prove that += for lists is not an accident: >>> a = set() >>> b = a >>> a |= set([1]) >>> a set([1]) >>> b set([1]) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
