已知有20个学生记录（包括学号，姓名，成绩等） 设计三个查找算法，分别实现按学号、姓名、成绩的折半查找； 菜单选择查找方式；

好的，下面是三个查找算法的实现：

1. 按学号的折半查找

def binary_search_by_id(records, target_id):
    left = 0
    right = len(records) - 1
    while left <= right:
        mid = (left + right) // 2
        if records[mid]['id'] == target_id:
            return mid
        elif records[mid]['id'] < target_id:
            left = mid + 1
        else:
            right = mid - 1
    return -1

2. 按姓名的折半查找

def binary_search_by_name(records, target_name):
    left = 0
    right = len(records) - 1
    while left <= right:
        mid = (left + right) // 2
        if records[mid]['name'] == target_name:
            return mid
        elif records[mid]['name'] < target_name:
            left = mid + 1
        else:
            right = mid - 1
    return -1

3. 按成绩的折半查找

def binary_search_by_score(records, target_score):
    left = 0
    right = len(records) - 1
    while left <= right:
        mid = (left + right) // 2
        if records[mid]['score'] == target_score:
            return mid
        elif records[mid]['score'] < target_score:
            left = mid + 1
        else:
            right = mid - 1
    return -1

然后，可以通过菜单选择不同的查找方式：

def search_menu(records):
    while True:
        print('请选择查找方式：')
        print('1. 按学号查找')
        print('2. 按姓名查找')
        print('3. 按成绩查找')
        print('4. 退出')
        choice = input('请输入选项：')
        if choice == '1':
            target_id = input('请输入要查找的学号：')
            index = binary_search_by_id(records, target_id)
            if index == -1:
                print('未找到记录')
            else:
                print('找到记录：', records[index])
        elif choice == '2':
            target_name = input('请输入要查找的姓名：')
            index = binary_search_by_name(records, target_name)
            if index == -1:
                print('未找到记录')
            else:
                print('找到记录：', records[index])
        elif choice == '3':
            target_score = input('请输入要查找的成绩：')
            index = binary_search_by_score(records, target_score)
            if index == -1:
                print('未找到记录')
            else:
                print('找到记录：', records[index])
        elif choice == '4':
            break
        else:
            print('无效选项，请重新输入')

注意，这里的 `records` 是一个包含所有学生记录的列表，每个记录是一个字典，包含学号、姓名、成绩等信息。