自学Python，编写了一个学生信息统计的小Demo。

import os

filename = 'student.txt'

def menum():
    print("==========================学生管理信息=============")
    print("------------------------------功能菜单--------------")
    print("\t\t\t\t\t\t\t1.录入学生信息")
    print("\t\t\t\t\t\t\t2.查找学生信息")
    print("\t\t\t\t\t\t\t3.删除学生信息")
    print("\t\t\t\t\t\t\t4.修改学生信息")
    print("\t\t\t\t\t\t\t5.排序")
    print("\t\t\t\t\t\t\t6.统计学生总人数")
    print("\t\t\t\t\t\t\t7.显示学生信息")
    print("\t\t\t\t\t\t\t0.退出系统")
    print("--------------------------------------------------")

def main():
    while True:
        menum()
        choice = int(input('请选择'))
        if choice in range(0,8):
            if choice == 0:
                answer = input("您确定要退出系统吗?y/n")
                if answer == 'y' or answer == 'Y':
                    print('谢谢您的使用！！！')
                    break
                else:
                    continue
            elif choice == 1:
                insert()
            elif choice == 2:
                search()
            elif choice == 3:
                delete()
            elif choice == 4:
                modify()
            elif choice == 5:
                sort()
            elif choice == 6:
                total()
            elif choice == 7:
                show()
    pass

def insert():
    student_list = []
    while True:
        id = input('请输入ID(如1001):')
        if not id:
            break
        name = input('请输入学生姓名:')
        if not name:
            break
        try:
            english = float(input('请输入english成绩:'))
            python = float(input('请输入python成绩:'))
            java = float(input('请输入java成绩:'))
        except:
            print('输入成绩无效,请重新输入')
        student_info = {'id':id,'name':name,'english':english,'python':python,'java':java}
        student_list.append(student_info)
        answer = input("是否继续添加?y/n\n")
        if answer == 'y' or answer == 'Y':
            continue
        else:
            break
    save(student_list)
    print('录入完毕')

def save(lst):
    try:
        stu_txt = open(filename, 'a', encoding='utf-8')
    except:
        stu_txt = open(filename, 'w', encoding='utf-8')
    for item in lst:
        stu_txt.write(str(item)+'\n')
    stu_txt.close()

def search():
    student_query = [];
    while True:
        id = ''
        name = ''
        if os.path.exists(filename):
            mode = input('ID查找请输入1，Name查找请输入2')
            if int(mode) == 1:
                id = input('请输入学生ID')
            elif int(mode) == 2:
                name = input('请输入学生Name')
            else:
                print('不支持此类型查询')
                search()
            with open(filename,'r',encoding='utf-8') as rFile:
                student = rFile.readlines()
                for item in student:
                    d = dict(eval(item))
                    if d!='':
                        if d['id'] == id:
                            student_query.append(d)
                    elif name!='':
                        if d['name'] == name:
                            student_query.append(d)
            show_student(student_query)
            student_query.clear()
            answer = input('是否继续查询?y/n\n')
            if answer=='y' or answer=='Y':
                continue
            else:
                break
        else:
            print('暂未保存学生信息')
            return

def show_student(lst):
    if len(lst) == 0:
        print('无数据')
        return
    format_title = '{:^6}\t{:^12}\t{:^8}\t{:^10}\t{:^10}\t{:^8}\t'
    print(format_title.format('ID','姓名','英语成绩','Python成绩','Java成绩','总成绩'))
    format_data = '{:^6}\t{:^12}\t{:^8}\t{:^10}\t{:^10}\t{:^8}\t'
    for item in lst:
        print(format_data.format(item.get('id'),
                                 item.get('name'),
                                 item.get('english'),
                                 item.get('python'),
                                 item.get('java'),
                                 float(item.get('english'))+float(item.get('python'))+float(item.get('java'))
                                 ))

def delete():
    while True:
        student_id = input('请输入学生ID：')
        if student_id != '':
            if os.path.exists(filename):
                with open(filename,'r',encoding='utf-8') as file:
                    student_old = file.readlines()
            else:
                student_old = []
            flag = False
            if student_old:
                with open(filename,'w',encoding='utf-8') as wfile:
                    d = {}
                    for item in student_old:
                        d = dict(eval(item))
                        if d['id'] != student_id:
                            wfile.write(str(d)+'\n')
                        else:
                            flag = True
                    if flag:
                        print(f'id为{student_id}的学生信息已被删除')
                    else:
                        print(f'id为{student_id}的学生信息不存在')
            else:
                print('无学生信息')
                break
            show()
            answer = input('是否继续删除?y/n\n')
            if answer=='y' or answer=='Y':
                continue
            else:
                break

def modify():
    while True:
        show()
        if os.path.exists(filename):
            with open(filename,'r',encoding='utf-8') as rfile:
                student_old = rfile.readlines()
        else:
            return
        student_id = input('请输入学生ID')
        with open(filename,'w',encoding='utf-8') as wfile:
                for item in student_old:
                    d = dict(eval(item))
                    if d['id'] == student_id:
                        print('找到学生信息,可以进行修改操作了')
                        while True:
                            try:
                                d['name'] = input('请输入学生姓名')
                                d['english'] = input('请输入english成绩')
                                d['python'] = input('请输入python成绩')
                                d['java'] = input('请输入java成绩')
                            except:
                                print("输入信息有误")
                            else:
                                break
                        wfile.write(str(d)+'\n')
                        print('修改成功')
                    else:
                        wfile.write(str(d)+'\t')
                answer = input('是否继续修改其他学生信息?y/n\n')
                if answer=='y' or answer=='Y':
                    modify()
                else:
                    break

def sort():
    if os.path.exists(filename):
        with open(filename,'r',encoding='utf-8') as rfile:
            student_new = []
            student_list = rfile.readlines()
            for item in student_list:
                d = dict(eval(item))
                student_new.append(d)
    else:
        return
    asc_or_desc = input('请选择排序方式0asc1desc')
    if asc_or_desc == '0':
        asc_or_desc_bool = False
    elif asc_or_desc == '1':
        asc_or_desc_bool = True
    else:
        print('输入有误')
        sort()
    mode = input('选择详细排序方式1English2Python3Java0Total')
    if mode == '1':
        student_new.sort(key=lambda self:float(self['english']),reverse=asc_or_desc_bool)
    elif mode == '2':
        student_new.sort(key=lambda self: float(self['python']), reverse=asc_or_desc_bool)
    elif mode == '3':
        student_new.sort(key=lambda self: float(self['java']), reverse=asc_or_desc_bool)
    elif mode == '4':
        student_new.sort(key=lambda self: (float(self['java'])+float(self['python'])+float(self['english'])), reverse=asc_or_desc_bool)
    else:
        print('详细排序输入有误')
        sort()
    show_student(student_new)

def total():
    if os.path.exists(filename):
        with open(filename,'r',encoding='utf-8') as rfile:
            students = rfile.readlines()
            if students:
                print('一共有{}名学生'.format(len(students)))
            else:
                print('没有学生信息')
    else:
        print('无数据')

def show():
    student_info = []
    if os.path.exists(filename):
        with open(filename,'r',encoding='utf-8') as rfile:
            students = rfile.readlines()
            for item in students:
                student_info.append(eval(item))
            if students:
                show_student(student_info)
            else:
                print('信息为空')
    else:
        print('文件不存在')


if __name__ == '__main__':
    main()