Multiple assignment semantics

In Python one can do:

a, b   = 1, 2
(a, b) = 1, 2
[a, b] = 1, 2

I checked the generated bytecode using dis and they are identical.
So why allow this at all? Would I ever need one of these instead of the others?

_{See also Multiple assignment and evaluation order in Python regarding the basic semantics of this kind of assignment.}

_{See also Understand Python swapping: why is a, b = b, a not always equivalent to b, a = a, b? for more complex cases, where the order of assignment matters.}

Solution

One case when you need to include more structure on the left hand side of the assignment is when you're asking Python unpack a slightly more complicated sequence. E.g.:

# Works
>>> a, (b, c) = [1, [2, 3]]

# Does not work
>>> a, b, c = [1, [2, 3]]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 2 values to unpack

This has proved useful for me in the past, for example, when using enumerate to iterate over a sequence of 2-tuples. Something like:

>>> d = { 'a': 'x', 'b': 'y', 'c': 'z' }
>>> for i, (key, value) in enumerate(d.iteritems()):
...     print (i, key, value)
(0, 'a', 'x')
(1, 'c', 'z')
(2, 'b', 'y')