At 11:16 PM 7/13/2010, Vern Ceder wrote: Actually this behavior has been in Python since augmented assignments were introduced in version 2.0. The official wording on this (buried in the language reference) is (2.7 version, emphasis mine): Vern, I was comparing Python 3 with 2.5; the latter doesn't seem to do += for lists in place. Gary Litvin