The clue is to work with the dict's items (i.e. key-value pair tuples). Then by using the second element of the item as the max key (as opposed to the dict key) you can easily extract the highest value and its associated key.
mydict = {'A':4,'B':10,'C':0,'D':87}
>>> max(mydict.items(), key=lambda k: k[1])
('D', 87)
>>> min(mydict.items(), key=lambda k: k[1])
('C', 0)
