('a', 'b', 'c')

 >>>
>>>
>>> color_mix = {}
>>>
>>> color_mix['red', 'blue'] = 'purple'          # works without parentheses
>>>
>>> color_mix[('blue', 'yellow')] = 'green'      # although it's customary to use them
>>>
>>> color_mix['yellow', 'red'] = 'orange'
>>>
>>> for k in color_mix.keys():
...     print k
...
('blue', 'yellow')
('red', 'blue')
('yellow', 'red')
>>>
>>>

 >>>
>>> tuple1 = ('cat', 'dog')
>>> tuple2 = ('dog', 'rat')
>>> tuple3 = ('cat', 'dog')
>>>
>>> tuple1 == tuple2
False
>>>
>>> tuple1 == tuple3
True
>>>
>>> ('hog', 'eel') == tuple1    # Works like this too
False
>>>
>>>

 >>>
>>> 'hog', 'eel' == tuple3      # Nope! Not what you would expect!
('hog', False)
>>>
>>> ('hog', 'eel') == ('dog', 'rat')  # Use parentheses to avoid surprises
False
>>>
>>>