On Wed, Jun 22, 2011 at 4:45 PM, Chetan Harjani <chetan.harj...@gmail.com> wrote: > why tuples are immutable whereas list are mutable? Because an immutable data type was needed, and a mutable type was also needed ;)
> why when we do x=y where y is a list and then change a element in x, y > changes too( but the same is not the case when we change the whole value in > x ), whereas, in tuples when we change x, y is not affected and also we cant > change each individual element in tuple. Someone please clarify. That's because y points to an object. When you assign x = y, you say "assign name x to object that's also pointed to by name y". When you change the list using list methods, you're changing the actual object. Since x and y both point to the same object, they both change. However, if you then assign y = [1], name y no longer points to the original object. x still remains pointing to the original object. >>> a = [1,2] # assign name a to object [1,2] >>> b = a # assign name b to object referred to by name a >>> b [1, 2] >>> a = [3,4] # assign name a to object [3,4] >>> b [1, 2] >>> a [3, 4] -- http://mail.python.org/mailman/listinfo/python-list
