Note item 6 of http://docs.python.org/2.7/library/stdtypes.html#mutable-sequence-types is a bit misleading.  

It states: "The pop() method is only supported by the list and array types. The optional argument i defaults to -1, so that by default the last item is removed and returned."  

However, pop() is also a method of sets, which are neither lists or arrays.