Two contradictory opinions from me :-) 1) multiplying a list or a bumpy array be an integer are very different operations — and in most cases, the result will be a different size (and type), which is the case in this example. So it’s rarely a hard to find bug. So that’s not a very compelling argument for this change. 2) this is surprising result that I’d pretty surprised that much code is using on purpose. So I’d think that it would make sense to have it raise an exception. Unless of course, someone does come up with some evidence that there is code in the wild that is counting on it working this way. BTW: to the OP: yes, Python can change, but we do try to keep breaking changes to an absolute minimum, and any breaking change needs to be very compelling— this really isn’t that. In fact, I don’t think there’s been a breaking change since the Py3 transition. I think PEP 563 was going to be the first — and that’s been delayed. -CHB -- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython