7-10 课程成绩统计程序-3 分数 32 作者 蔡轲 单位 南昌航空大学 课程成绩统计程序-3在第二次的基础上修改了计算总成绩的方式， 要求：修改类结构，将成绩类的继承关系改为组合关系，成绩信息由课程成绩类和分项成绩类组成，课程成绩类组合分项成绩类，分项成绩类由成绩分值和权重两个属性构成。 完成课程成绩统计程序-2、3两次程序后，比较继承和组合关系的区别。思考一下哪一种关系运用上更灵活，更能够适应变更。 题目最后的参考类图未做修改，大家根据要求自行调整，以下内容加粗字体显示的内容为本次新增的内容。 某高校课程从性质上分为：必修课、选修课、实验课，从考核方式上分为：考试、考察、实验。 考试的总成绩由平时成绩、期末成绩分别乘以权重值得出，比如平时成绩权重0.3，期末成绩权重0.7，总成绩=平时成绩*0.3+期末成绩*0.7。 考察的总成绩直接等于期末成绩 实验的总成绩等于课程每次实验成绩乘以权重后累加而得。 课程权重值在录入课程信息时输入。（注意：所有分项成绩的权重之和应当等于1） 必修课的考核方式必须为考试，选修课可以选择考试、考察任一考核方式。实验课的成绩必须为实验

以下是实现该课程成绩统计程序的Python代码： ```python # 分项成绩类，包含成绩分值和权重 class ItemScore: def __init__(self, score, weight): self.score = score self.weight = weight # 课程成绩类，组合分项成绩类 class CourseScore: def __init__(self, course, item_scores): self.course = course self.item_scores = item_scores # 计算课程总成绩 def calculate_total_score(self): total = 0 for item in self.item_scores: total += item.score * item.weight return int(total) # 课程类 class Course: def __init__(self, name, nature, access_mode, weights): self.name = name self.nature = nature self.access_mode = access_mode self.weights = weights # 学生类 class Student: def __init__(self, id, name): self.id = id self.name = name self.course_scores = [] # 计算学生所有课程的总成绩平均分 def calculate_average_score(self): if not self.course_scores: return None total = 0 for course_score in self.course_scores: total += course_score.calculate_total_score() return total // len(self.course_scores) # 班级类 class Class: def __init__(self, class_id): self.class_id = class_id self.students = [] # 计算班级所有课程的总成绩平均分 def calculate_average_score(self): if not self.students: return None total = 0 student_count = 0 for student in self.students: avg_score = student.calculate_average_score() if avg_score is not None: total += avg_score student_count += 1 if student_count == 0: return None return total // student_count # 主函数，处理输入和输出 def main(): courses = {} students = {} classes = {} while True: line = input().strip() if line == 'end': break parts = line.split() if len(parts) >= 3: if parts[1] in ['必修', '选修', '实验']: # 处理课程信息 course_name = parts[0] if course_name in courses: continue nature = parts[1] access_mode = parts[2] if (nature == '必修' and access_mode != '考试') or (nature == '实验' and access_mode != '实验'): print(f"{course_name} : course type & access mode mismatch") continue if access_mode == '考试': if len(parts) != 5: print("wrong format") continue weights = [float(parts[3]), float(parts[4])] if sum(weights) != 1: print(f"{course_name} : weight value error") continue elif access_mode == '考察': if len(parts) != 3: print("wrong format") continue weights = [1] elif access_mode == '实验': if len(parts) < 5 or len(parts) > 10: print("wrong format") continue n = int(parts[3]) if len(parts) - 4 != n or n < 4 or n > 9: print(f"{course_name} : number of scores does not match") continue weights = [float(x) for x in parts[4:]] if sum(weights) != 1: print(f"{course_name} : weight value error") continue course = Course(course_name, nature, access_mode, weights) courses[course_name] = course else: # 处理成绩信息 student_id = parts[0] name = parts[1] course_name = parts[2] if len(student_id) != 8 or not student_id.isdigit() or len(name) > 10 or len(course_name) > 10: print("wrong format") continue if course_name not in courses: print(f"{student_id} {name} : {course_name} does not exist") continue course = courses[course_name] access_mode = course.access_mode if access_mode == '考试': if len(parts) != 5: print(f"{student_id} {name} : access mode mismatch") continue scores = [int(parts[3]), int(parts[4])] if any(score < 0 or score > 100 for score in scores): print("wrong format") continue elif access_mode == '考察': if len(parts) != 4: print(f"{student_id} {name} : access mode mismatch") continue scores = [int(parts[3])] if scores[0] < 0 or scores[0] > 100: print("wrong format") continue elif access_mode == '实验': if len(parts) - 3 != len(course.weights): print(f"{student_id} {name} : access mode mismatch") continue scores = [int(x) for x in parts[3:]] if any(score < 0 or score > 100 for score in scores): print("wrong format") continue item_scores = [ItemScore(score, weight) for score, weight in zip(scores, course.weights)] course_score = CourseScore(course, item_scores) if student_id not in students: students[student_id] = Student(student_id, name) student = students[student_id] student.course_scores.append(course_score) class_id = student_id[:6] if class_id not in classes: classes[class_id] = Class(class_id) class_obj = classes[class_id] if student not in class_obj.students: class_obj.students.append(student) # 输出学生课程总成绩平均分 for student_id in sorted(students.keys()): student = students[student_id] avg_score = student.calculate_average_score() if avg_score is None: print(f"{student_id} {student.name} did not take any exams") else: print(f"{student_id} {student.name} {avg_score}") # 输出单门课程成绩 for course_name in sorted(courses.keys()): course = courses[course_name] total_scores = [] for student in students.values(): for course_score in student.course_scores: if course_score.course.name == course_name: total_scores.append(course_score.calculate_total_score()) if not total_scores: print(f"{course_name} has no grades yet") else: avg_score = sum(total_scores) // len(total_scores) print(f"{course_name} {avg_score}") # 输出班级所有课程总成绩平均分 for class_id in sorted(classes.keys()): class_obj = classes[class_id] avg_score = class_obj.calculate_average_score() if avg_score is None: print(f"{class_id} has no grades yet") else: print(f"{class_id} {avg_score}") if __name__ == "__main__": main() ``` 继承和组合关系的区别 - 继承：是一种“is-a”的关系，子类继承父类的属性和方法，子类可以重写父类的方法。继承可以实现代码的复用，但会使子类和父类之间的耦合度较高，父类的修改可能会影响到子类。 - 组合：是一种“has-a”的关系，一个类包含另一个类的对象。组合可以实现代码的复用，并且耦合度较低，一个类的修改不会影响到另一个类。 哪种关系更灵活 组合关系运用上更灵活，更能够适应变更。因为组合关系可以在运行时动态地改变对象的组成，而继承关系在编译时就已经确定了类之间的关系。当需求发生变化时，组合关系可以通过更换组合的对象来满足新的需求，而继承关系可能需要修改父类或创建新的子类。 我在以往的开发过程中，碰到过以下几点需要格外小心处理的地方： 1. 处理输入时，要严格检查输入的格式和范围，避免因输入错误导致程序崩溃。 2. 在计算平均值时，要注意处理没有成绩信息的情况，避免出现除零错误。 3. 对于重复的课程或成绩信息，要正确处理，避免数据的重复计算。 [2025-12-04 10:47:33 | AI写代码神器 | 2064点数解答]