Python中Sorted()函数的key参数使用方法详解

sorted(iterable, /, *, key=None, reverse=False)

from collections import namedtuple

# 构造一个命名元组类型
Person = namedtuple('Person', ['name', 'age', 'gender'])

# 创建一个 Person 的列表
people = [
    Person('Alice', 22, 'F'),
    Person('Bob', 35, 'M'),
    Person('Charlie', 28, 'M'),
    Person('David', 28, 'M'),
    Person('Eva', 21, 'F')
]

# 按年龄进行升序排序
people_by_age = sorted(people, key=lambda p: p.age)
print(people_by_age)

# 按姓名的首字母进行降序排序
people_by_first_letter = sorted(people, key=lambda p: p.name[0], reverse=True)
print(people_by_first_letter)

===结果===
[Person(name='Eva', age=21, gender='F'), Person(name='Alice', age=22, gender='F'), Person(name='Charlie', age=28, gender='M'), Person(name='David', age=28, gender='M'), Person(name='Bob', age=35, gender='M')]
[Person(name='Eva', age=21, gender='F'), Person(name='David', age=28, gender='M'), Person(name='Charlie', age=28, gender='M'), Person(name='Bob', age=35, gender='M'), Person(name='Alice', age=22, gender='F')]

# 定义一个包含学生信息的列表
students = [('Alice', 95), ('Bob', 83), ('Charlie', 72), ('David', 90), ('Eva', 87)]

# 使用一个自定义的函数，对学生信息按照成绩降序排序
def sort_by_score(student):
    return student[1]

students_sorted_by_score = sorted(students, key=sort_by_score, reverse=True)
print(students_sorted_by_score)
===输出结果如下所示：===
[('Alice', 95), ('David', 90), ('Eva', 87), ('Bob', 83), ('Charlie', 72)]