On Thursday, December 21, 2017 at 7:37:39 AM UTC-8, MRAB wrote: > Python never makes a copy unless you ask it to. > > What x1=X does is make the name x1 refer to the same object that X > refers to. No copying.
Well, except with very simple, mutable data types like scalars... compare this: >>> x=5 >>> y=x >>> x,y (5, 5) >>> x+=1 >>> x,y (6, 5) To this: >>> a=[1,2,3] >>> b=a >>> a,b ([1, 2, 3], [1, 2, 3]) >>> a[1]=9 >>> a,b ([1, 9, 3], [1, 9, 3]) -- https://mail.python.org/mailman/listinfo/python-list
