Python文件处理问题

score1里面第一个是学号，学号前两位是年级，然后是名字，专业班级，分数。
问题如图，希望大神解答一下

data = {}
with open('score_1.txt', 'r') as f:
    student = f.readline().replace('\n', '')
    while student:
        Student_number, name, class_name, score = student.split(',')
        Grade = Student_number[:2]
        if data.get(Grade):
            data[Grade].append([Student_number, name, class_name, float(score)])
        else:
            data[Grade] = [[Student_number, name, class_name, float(score)]]

for i in data.keys():
    print(i, "级有", len(data[i]), "人")
    print(i, "级平均成绩", sum([Student[-1] for Student in data[i]]) / len(data[i]))
    print(i, "级平不及格", len([Student for Student in data[i] if Student[-1] < 60]), "人")

没有数据文档,也只有这样了,不能运行在找我