>>> import dis
>>> def f():
...   a = ['a']
...   b = ['b']
...   c = [a, b]
...   a, a[0] = b, a[0]
...
>>> dis.dis(f)
  2           0 LOAD_CONST               1 ('a')
              3 BUILD_LIST               1
              6 STORE_FAST               0 (a)

  3           9 LOAD_CONST               2 ('b')
             12 BUILD_LIST               1
             15 STORE_FAST               1 (b)

  4          18 LOAD_FAST                0 (a)
             21 LOAD_FAST                1 (b)
             24 BUILD_LIST               2
             27 STORE_FAST               2 (c)

  5          30 LOAD_FAST                1 (b)
             33 LOAD_FAST                0 (a)
             36 LOAD_CONST               3 (0)
             39 BINARY_SUBSCR
             40 ROT_TWO
             41 STORE_FAST               0 (a)
             44 LOAD_FAST                0 (a)
             47 LOAD_CONST               3 (0)
             50 STORE_SUBSCR
             51 LOAD_CONST               0 (None)
             54 RETURN_VALUE