Python MOOC学生数据库练习：add_course函数重复课程成绩处理问题求助

作为Python新手，在完成「学生数据库练习-第三部分」时遇到问题：编写的add_course函数无法忽略添加成绩更低的重复课程，运行代码后会产生重复课程条目。期望实现：若学生已存在某课程，重复添加时仅保留最高成绩，不降低原有记录。

原代码核心问题 #

原代码中elif course[0] in courses:的判断逻辑错误。courses是存储(课程名, 成绩)元组的列表，直接用课程名字符串判断是否在列表中，永远会返回False，导致重复课程被不断添加。

修改后的解决方案 #

修正后的add_course函数 #

def add_course(database: dict, name: str, course: tuple):
    courses = database[name]
    course_name, new_grade = course
    # 跳过成绩为0的课程
    if new_grade == 0:
        return
    # 遍历现有课程，检查是否存在同名课程
    for i, (existing_name, existing_grade) in enumerate(courses):
        if existing_name == course_name:
            # 仅当新成绩更高时更新原有记录
            if new_grade > existing_grade:
                courses[i] = course
            return
    # 未找到同名课程，添加新条目
    courses.append(course)

完整运行代码 #

# Write your solution here
def add_student(database: dict, name: str):
    courses = []
    database[name] = courses

def add_course(database: dict, name: str, course: tuple):
    courses = database[name]
    course_name, new_grade = course
    if new_grade == 0:
        return
    for i, (existing_name, existing_grade) in enumerate(courses):
        if existing_name == course_name:
            if new_grade > existing_grade:
                courses[i] = course
            return
    courses.append(course)
    
def print_student(database: dict, name: str):
    if name not in database:
        print(f"{name}: no such person in the database")
    else:
        courses = database[name]
        if len(courses) == 0:
            print(f"{name}:")
            print(" no completed courses")
        else:
            sum_grades = 0
            print(f"{name}:")
            print(f" {len(courses)} completed courses:")
            for course_name, grade in courses:
                sum_grades += grade
                print(f"  {course_name} {grade}")
            avg_grade = sum_grades / len(courses)
            print(f" average grade {avg_grade}")

if __name__ == "__main__":
    students = {}
    add_student(students, "Peter")
    add_course(students, "Peter", ("Introduction to Programming", 3))
    add_course(students, "Peter", ("Advanced Course in Programming", 2))
    add_course(students, "Peter", ("Data Structures and Algorithms", 0))
    add_course(students, "Peter", ("Introduction to Programming", 2))
    print_student(students, "Peter")

关键改动说明 #

1. 拆分课程元组为单独的名称和成绩变量，提升逻辑可读性；
2. 使用enumerate遍历课程列表，同时获取索引和课程信息，方便后续更新原有记录；
3. 找到同名课程时，仅在新成绩更高的情况下替换原有条目；
4. 对print_student函数做了小优化：提前取出课程列表变量，将平均成绩计算移至循环外（避免冗余计算）。

运行结果 #

运行代码后，不会出现重复课程条目，且保留最高成绩，输出如下：

Peter:
 2 completed courses:
  Introduction to Programming 3
  Advanced Course in Programming 2
 average grade 2.5

内容的提问来源于stack exchange，提问作者Antoniorodr