>>> t = ('a', 'b')
>>> dct = dict((t,))
>>> dct
{'a': 'b'}
>>>

>>> dct = {}
>>> 
>>> t = ('a', 'b')
>>> dct.update((t,))
>>> 
>>> t = ('c', 'd')
>>> dct.update((t,))
>>> 
>>> dct
{'a': 'b', 'c': 'd'}
>>>