Python之sort函数

a = [5,7,6,3,4,1,2]
b = sorted(a)       # 保留原列表
print(a) #[5, 7, 6, 3, 4, 1, 2]
print(b)  #[1, 2, 3, 4, 5, 6, 7]

L=[('b',2),('a',1),('c',3),('d',4)]
print(sorted(L, cmp=lambda x,y:cmp(x[1],y[1])))   # 利用cmp函数
#[('a', 1), ('b', 2), ('c', 3), ('d', 4)]
print(sorted(L, key=lambda x:x[1]))               # 利用key
#[('a', 1), ('b', 2), ('c', 3), ('d', 4)]


students = [('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]
print(sorted(students, key=lambda s: s[2]))            # 按年龄排序
#[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

print(sorted(students, key=lambda s: s[2], reverse=True))    # 按降序
#[('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]