如何按集合对集合进行分组？

# 假设有一个包含学生信息的集合
students = [
    {"name": "张三", "age": 18, "grade": "一年级"},
    {"name": "李四", "age": 19, "grade": "二年级"},
    {"name": "王五", "age": 18, "grade": "一年级"},
    {"name": "赵六", "age": 19, "grade": "二年级"}
]

# 创建一个空字典，用于存放分组结果
grouped_students = {}

# 遍历学生集合，按年级进行分组
for student in students:
    grade = student["grade"]
    if grade not in grouped_students:
        grouped_students[grade] = []
    grouped_students[grade].append(student)

# 打印分组结果
for grade, students in grouped_students.items():
    print(f"年级：{grade}")
    for student in students:
        print(f"姓名：{student['name']}，年龄：{student['age']}")
    print()