4.读取成绩文件grade.txt，自定义设计数据类型， （1）根据总评=0.7*期末+0.3*平时，计算出所有人成绩 （2）计算出不同教师的学生期末成绩平均分。

在Python中，我们可以创建一个自定义的数据类型，比如`Student`类，来表示学生的信息，包括姓名、教师和成绩等。首先，我们需要读取`grade.txt`文件，假设它是一个包含学生信息的CSV或文本文件，每行包含学生姓名、教师姓名和两门成绩（期末和平时）。

class Student:
    def __init__(self, name, teacher, final_exam, mid_term):
        self.name = name
        self.teacher = teacher
        self.final_exam = float(final_exam)
        self.mid_term = float(mid_term)

def load_students(file_path):
    students = []
    with open(file_path, 'r') as file:
        lines = file.readlines()
        for line in lines[1:]:  # skip header if present
            data = line.strip().split(',')
            name, teacher, final_exam, mid_term = data
            students.append(Student(name, teacher, final_exam, mid_term))
    return students

def calculate_total_grades(students):
    for student in students:
        total_grade = 0.7 * student.final_exam + 0.3 * student.mid_term
        print(f"{student.name} 的总评成绩为: {total_grade}")

def calculate_teacher_average(teacher, students):
    teacher_scores = [student.final_exam for student in students if student.teacher == teacher]
    if len(teacher_scores) > 0:
        average = sum(teacher_scores) / len(teacher_scores)
        print(f"教师{teacher}的学生期末平均分为: {average}")
    else:
        print(f"找不到教师{teacher}的学生")

# 读取文件并计算成绩
students = load_students('grade.txt')
calculate_total_grades(students)

# 计算不同教师的平均分
teachers = set([student.teacher for student in students])
for teacher in teachers:
    calculate_teacher_average(teacher, students)