"""
[('a', 3), ('b', 1), ('c', 2)] 按照中间元组的第二项排序
"""
def my_cmp(E1, E2):
return cmp(E1[1], E2[1]) #compare weight of each 2-tuple
#return the negative result of built-in cmp function
#thus we get the descend order
L = [('a',3),('b',1),('c',2)]
L.sort(my_cmp)
print L
list = [('a', 3), ('b', 1), ('c', 2)]
list.sort( key=lambda x: x[1] )
print list