python 对文件操作

#!/usr/bin/env python
# -*- coding:utf-8 -*-

def Find(class_name):
    class_list = []
    tag = False
    with open(‘data‘, ‘r‘, encoding=‘utf8‘) as f:
        for line in f:
            if line.strip() == ‘班级：{0}班‘.format(class_name.strip()):
                class_list.append(line)
                tag = True
                continue
            if tag and line.find(‘班级：‘) != 0:
                class_list.append(line)
            if line.find(‘班级：‘) == 0:
                tag = False

    return class_list;


def Add(dic):
    # { ‘班级‘:‘191‘,‘学生‘:[{‘姓名‘:‘张三‘,‘学号‘:‘2018001‘,‘年龄‘:18,‘性别‘:‘男‘},{‘姓名‘:‘李四‘,‘学号‘:‘2018002‘,‘年龄‘:21,‘性别‘:‘男‘},{‘姓名‘:‘小花‘,‘学号‘:‘2018003‘,‘年龄‘:18,‘性别‘:‘女‘},{‘姓名‘:‘小红‘,‘学号‘:‘2018004‘,‘年龄‘:33,‘性别‘:‘女‘}]}
    class_obj = eval(dic)
    class_name = class_obj[‘班级‘]
    class_list = Find(class_name)
    if len(class_list) > 0:
        print(‘系统中已经存在班级[%s]。‘ % (class_name))
        return

    with open(‘data‘, ‘a+‘, encoding=‘utf8‘) as f:
        f.write(‘\n班级：%s班‘ % (class_name))
        for student in class_obj[‘学生‘]:
            f.write(‘\n    姓名：{0}   学号：{1}   年龄：{2}   性别：{3}‘.format(student[‘姓名‘], student[‘学号‘], student[‘年龄‘],
                                                                     student[‘性别‘]))

    print(‘添加成功！‘)


def Update(dic):
    class_obj = eval(dic)
    class_name = class_obj[‘班级‘]
    class_list = Find(class_name)
    if len(class_list) == 0:
        print(‘没有查询到该班级信息。‘)
        return
    Delete(class_name)
    Add(dic)
    print(‘更新成功！‘)


def Delete(class_name):
    class_list = Find(class_name)
    if len(class_list) == 0:
        print(‘没有查询到该班级信息。‘)
        return
    class_list = []
    tag = False
    with open(‘data‘, ‘r‘, encoding=‘utf8‘) as old_file:
        for line in old_file:
            if line.strip() == ‘班级：{0}班‘.format(class_name.strip()):
                tag = True
                continue
            else:
                if tag and line.find(‘班级：‘) != 0:
                    continue
                if line.find(‘班级：‘) == 0:
                    tag = False
                class_list.append(line)

    with open(‘data‘, ‘w‘, encoding=‘utf8‘) as new_file:
        for line in class_list:
            new_file.write(line)

    print(‘删除成功！‘)


if __name__ == ‘__main__‘:
    while True:
        print(‘\n1、查询    2、修改    3、添加    4、删除    ‘)
        operation = input(‘请输入操作：‘)
        if (operation == ‘1‘):
            class_name = input(‘请输入查询的班级名称：‘)
            class_list = Find(class_name)
            if len(class_list) == 0:
                print(‘没有查询到该班级信息。‘)
            else:
                for line in class_list:
                    print(line, end=‘‘)
        elif (operation == ‘2‘):
            dic = input(‘请输入修改的字典数据：‘)
            Update(dic)
        elif (operation == ‘3‘):
            dic = input(‘请输入添加的字典数据：‘)
            Add(dic)
        elif (operation == ‘4‘):
            class_name = input(‘请输入删除的班级名称：‘)
            Delete(class_name)
        else:
            print("输入不正确")