Python assignment destructuring

Question

These three expressions seem to be equivalent:

a,b,c = line.split() (a,b,c) = line.split() [a,b,c] = line.split() 

Do they compile to the same code?

Which one is more pythonic?

Answer 1

According to dis, they all get compiled to the same bytecode:

>>> def f1(line): ...  a,b,c = line.split() ...  >>> def f2(line): ...  (a,b,c) = line.split() ...  >>> def f3(line): ...  [a,b,c] = line.split() ...  >>> import dis >>> dis.dis(f1)   2           0 LOAD_FAST                0 (line)               3 LOAD_ATTR                0 (split)               6 CALL_FUNCTION            0               9 UNPACK_SEQUENCE          3              12 STORE_FAST               1 (a)              15 STORE_FAST               2 (b)              18 STORE_FAST               3 (c)              21 LOAD_CONST               0 (None)              24 RETURN_VALUE         >>> dis.dis(f2)   2           0 LOAD_FAST                0 (line)               3 LOAD_ATTR                0 (split)               6 CALL_FUNCTION            0               9 UNPACK_SEQUENCE          3              12 STORE_FAST               1 (a)              15 STORE_FAST               2 (b)              18 STORE_FAST               3 (c)              21 LOAD_CONST               0 (None)              24 RETURN_VALUE         >>> dis.dis(f3)   2           0 LOAD_FAST                0 (line)               3 LOAD_ATTR                0 (split)               6 CALL_FUNCTION            0               9 UNPACK_SEQUENCE          3              12 STORE_FAST               1 (a)              15 STORE_FAST               2 (b)              18 STORE_FAST               3 (c)              21 LOAD_CONST               0 (None)              24 RETURN_VALUE         

So they should all have the same efficiency. As far as which is most Pythonic, it's somewhat down to opinion, but I would favor either the first or (to a lesser degree) the second option. Using the square brackets is confusing because it looks like you're creating a list (though it turns out you're not).