Python基础第六天

一、内容

二、练习

练习1

题目：文件的增删改查

图示：

代码：

import os

def add(data):
    content = data[1]   # 文件内容
    file_name = data[-1]# 文件名
    with open(file_name,'r',encoding='utf-8') as f_read:
        lines = f_read.readlines()
    with open('b.txt','a',encoding='utf-8') as f_write:
        for line in lines:
            f_write.write(line)
        f_write.write(content)
    os.remove(file_name)
    os.rename('b.txt',file_name)
    with open('b.txt','w',encoding='utf-8') as f:
        pass

def delete(data):
    content = data[1]    # 文件内容
    file_name = data[-1] # 文件名
    with open(file_name,'r',encoding='utf-8') as f_read:
        lines = f_read.readlines()
    with open('b.txt','w',encoding='utf-8') as f_write:
        for line in lines:
            if content in line:
                continue
            f_write.write(line)
    os.remove(file_name)
    os.rename('b.txt',file_name)
    with open('b.txt','w',encoding='utf-8') as f:
        pass

def change(data):
    content = data[1]
    file_name = data[-1]
    with open(file_name,'r',encoding='utf-8') as f_read:
        lines = f_read.readlines()
    with open('b.txt','w',encoding='utf-8') as f_write:
        user_change_content = input('Please enter new content:').strip()
        for line in lines:
            if content in line:
                f_write.write(user_change_content)
                f_write.write('
')
                continue
            f_write.write(line)
    os.remove(file_name)
    os.rename('b.txt', file_name)
    with open('b.txt','w',encoding='utf-8') as f:
        pass

def search(data):
    content = data[1]   # 文件内容
    file_name = data[-1]# 文件名
    with open(file_name,'r',encoding='utf-8') as f:
        for i,line in enumerate(f,1):
            if content in line:
                print(i,line)

user_dic = {
    'add':add,
    'delete':delete,
    'change':change,
    'search':search
}

while True:
    user = input('Please enter the command:').strip()
    user_l = user.split() # 将用户输入的命令进行切片，以空格为分隔符，得到一个列表
    if len(user_l) != 3:  # 当这个列表的参数小于3个提示用户缺少参数
        print('Missing parameters or Content not found!')
        continue
    if not user or not user_l[0] in user_dic: # 当用户输入为空或列表的第一个参数不在字典user_dic里时提示用户无效的输入
        print('Invalid input!')
        continue

    if user_l[0] in user_dic: # 当列表中的第一个元素在user_dic中时
        if os.path.exists(user_l[-1]):# 当列表中的最后一个元素（即用户输入的文件名）存在时
            user_dic[user_l[0]](user_l) # 调用相对应的函数功能，将列表当作实参进行传递
        else:
            print('The file you want to operate does not exist,please try again.')

输出结果：

a.txt原文件：