Unpacking a list / tuple of pairs into two lists / tuples

>>> source_list = [('1','a'),('2','b'),('3','c'),('4','d')]
>>> list1, list2 = zip(*source_list)
>>> list1
('1', '2', '3', '4')
>>> list2
('a', 'b', 'c', 'd')

Edit: Note that zip(*iterable) is its own inverse:

>>> list(source_list) == zip(*zip(*source_list))
True

When unpacking into two lists, this becomes:

>>> list1, list2 = zip(*source_list)
>>> list(source_list) == zip(list1, list2)
True

Addition suggested by rocksportrocker.

list1 = (x[0] for x in source_list)
list2 = (x[1] for x in source_list)