求教，看不懂算法
data = input() # 课程名 考分d = {}
while data:
t = data.split()
d[t[0]] = t[1]
data = input()
ls.sort(key=lambda x:x[1],reverse=True)
s1,g1 = ls[0]
s2,g2 = ls[len(ls)-1]
a = 0
for i in value():
a = a+int(i)
a=a/len(ls)
print("最高分课程是{} {}, 最低分课程是{} {}, 平均分是{:.2f}".format(s1,g1,s2,g2))
