I was solving a problem when I accidentally found this weird feature in python:

list1 = [1]
list1.append(list1)
print(list1[1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][1][0])

You can append a list to itself. This code prints 1.

list1 = []
list1.append(list1)
print(list1[0][0][0][0][0][0])

This will print [[...]]. I guess it prints this to show that the list tunnels on forever.

It makes sense but it still seems like an odd feature. I can't see how this would be useful.