#判断元素出现的次数、总和
#coding:utf-8
d=[('a', 2), ('a', 1), ('b', 2), ('b', 5), ('c', 1), ('d', 5)]
def main():
r ={}
for a,b in d:
t =r.get(a,{})
t['times']=t.get('times',0)+1
t['sum']=t.setdefault("sum",0)+b
r[a]=t
print r
if __name__ == '__main__':
main()
结果：
{'a': {'sum': 3, 'times': 2}, 'c': {'sum': 1, 'times': 1}, 'b': {'sum': 7, 'times': 2}, 'd': {'sum': 5, 'times': 1}}