python is less crazy than it seems

gistfile1.py

In [8]: def t():
    f = ([],)
    f[0] += [1]
    return f
   ...: 

In [9]: dis.dis(t)
  2           0 BUILD_LIST               0
              3 BUILD_TUPLE              1
              6 STORE_FAST               0 (f)

  3           9 LOAD_FAST                0 (f)
             12 LOAD_CONST               1 (0)
             15 DUP_TOPX                 2
             18 BINARY_SUBSCR       
             19 LOAD_CONST               2 (1)
             22 BUILD_LIST               1
             25 INPLACE_ADD         
             26 ROT_THREE           
             27 STORE_SUBSCR        

  4          28 LOAD_FAST                0 (f)
             31 RETURN_VALUE