What range function does to a Python list?

Question

I am not able to figure out what is happening here. Appending reference to range function is kind of creating a recursive list at index 3.

>>> x = range(3)
[0, 1, 2]
>>> x.append(x)
[0, 1, 2, [...]]
>>> x[3][3][3][3][0] = 5
[5, 1, 2, [...]]

Whereas, when I try this:

 >>> x = range(3)
 [0, 1, 2]
 >>> x.append(range(3))
 [0, 1, 2, [0, 1, 2]]

I can easily deduce the reason for the second case but not able to understand what appending reference to range function is doing to the list appended.

Answer 1

In python2, ranges are lists.

lists, and most of the things in python are objects with identities.

li = [0,1]
li[1] = li    # [0, [...]]
              # ^----v
id(li)        # 2146307756
id(li[1])     # 2146307756

Since you're putting the list inside itself, you're creating a recursive data structure.