access to the last element of an array in python

opcodes.txt

>>> a = [1, 2, 3]
>>> import dis
>>> def f():
        print a[len(a)-1]
... ...
>>> def g():
        print a[-1]
... ...
>>> dis.dis(f)
  2           0 LOAD_GLOBAL              0 (a)
              3 LOAD_GLOBAL              1 (len)
              6 LOAD_GLOBAL              0 (a)
              9 CALL_FUNCTION            1
             12 LOAD_CONST               1 (1)
             15 BINARY_SUBTRACT
             16 BINARY_SUBSCR
             17 PRINT_ITEM
             18 PRINT_NEWLINE
             19 LOAD_CONST               0 (None)
             22 RETURN_VALUE
>>> dis.dis(g)
  2           0 LOAD_GLOBAL              0 (a)
              3 LOAD_CONST               1 (-1)
              6 BINARY_SUBSCR
              7 PRINT_ITEM
              8 PRINT_NEWLINE
              9 LOAD_CONST               0 (None)
             12 RETURN_VALUE