python中operator.itemgetter函數

operator模塊提供的itemgetter函數用於獲取對象的哪些維的數據，參數為一些序號（即需要獲取的數據在對象中的序號），下面看例子。

k = [3,6,8]
b = operator.itemgetter(1)
print(b(k))
#輸出6

k = [3,6,8]
b = operator.itemgetter(2,0)
print(b(k))
#輸出(8, 3)

要注意，operator.itemgetter函數獲取的不是值，而是定義了一個函數，通過該函數作用到對象上才能獲取值。

students = [('john', 'C', 15), ('jane', 'A', 12), ('dave', 'B', 10)]
s = sorted(students,key = operator.itemgetter(1,2))
print(s)
#輸出[('jane', 'A', 12), ('dave', 'B', 10), ('john', 'C', 15)]

看看下面的練習

Q：找到年齡最大的人，並輸出，person = {"li":18,"wang":50,"zhang":20,"sun":22}

常規for循環解法

def fun(person):
    max = 0
    name = ""
    for key,value in person.items():
        if value > max:
            max = value
            name = key
    print(name)
    print(max)
fun(person)

利用operator.itemgetter函數

import operator
person = {"li":18,"wang":50,"zhang":20,"sun":22}
print(max(person.values()))
print(max(person.items(),key = operator.itemgetter(1))[0])  # 獲取最大值的 key