>>> a_dict = {'aa1':'n','ba2' : 'a','aa2':'a'}
>>> a_dict
{'ba2': 'a', 'aa1': 'n', 'aa2': 'a'}

>>> b_tuple = sorted(a_dict.items(),key = lambda x: x[1])
>>> b_tuple
[('ba2', 'a'), ('aa2', 'a'), ('aa1', 'n')]