On Wednesday, June 8, 2016 at 4:32:33 PM UTC+5:30, Antoon Pardon wrote: > It means that if you mutate the object through one variable, > you can see the result of that mutation through the other variable. But if the > assignment doesn't mutate, you can't have such effect through assignment. >
Its called aliasing: https://en.wikipedia.org/wiki/Aliasing_%28computing%29 And is the principal reason why we need to talk in terms of pointer/references/box-n-arrows etc > In python, you can sometimes simulate a mutating assignment and then we get > this. > > >>> A = [8, 5, 3, 2] > >>> B = A > >>> B[:] = [3, 5, 8, 13] > >>> A > [3, 5, 8, 13] Neat example -- thanks -- something for my tomorrow class More telling than the one I usually use to talk of this stuff which runs thus: >>> a=[[1,2,],[1,2]] >>> a [[1, 2], [1, 2]] >>> inner=[1,2] >>> b=[inner,inner] >>> b [[1, 2], [1, 2]] # So a and b look the same >>> a == b True # So even python thinks them the same # But Uh... oh... >>> a[0][0]=3 >>> a [[3, 2], [1, 2]] >>> b[0][0]=3 >>> b [[3, 2], [3, 2]] # They dont behave the same! -- https://mail.python.org/mailman/listinfo/python-list
