题目一：编写文件修改功能

方法一：文本编辑采用的就是这种方式
实现思路：将文件内容发一次性全部读入内存,然后在内存中修改完毕后再覆盖写回原文件
优点: 在文件修改过程中同一份数据只有一份
缺点: 会过多地占用内存

def modify(modify_path, old_content, new_content):
    '''文件修改'''
    with open('{}'.format(modify_path),mode='rt',encoding='utf-8') as f:
        res=f.read()
        data=res.replace(old_content,new_content)
        print(data)
    with open('{}'.format(modify_path),mode='wt',encoding='utf-8') as f1:
        f1.write(data)


modify_path = input('输入要修改的文件路径：')
old_content = input('输入要修改的内容：')
new_content = input('输入修改后的内容：')
modify(modify_path, old_content, new_content)

方法二
实现思路：以读的方式打开原文件,以写的方式打开一个临时文件,一行行读取原文件内容,修改完后写入临时文件...,删掉原文件,将临时文件重命名原文件名
优点: 不会占用过多的内存
缺点: 在文件修改过程中同一份数据存了两份

import os


def modify(modify_path, old_content, new_content):
    '''文件修改'''
    with open(r'{}'.format(modify_path), mode='rt', encoding='utf-8') as f1, 
            open(r'.{}.swap'.format(modify_path), mode='wt', encoding='utf-8') as f2:
        for line in f1:
            f2.write(line.replace(old_content, new_content))
    os.remove(r'{}'.format(modify_path))
    os.rename(r'.{}.swap'.format(modify_path), r'{}'.format(modify_path))


modify_path = input('输入要修改的文件路径：')
old_content = input('输入要修改的内容：')
new_content = input('输入修改后的内容：')
modify(modify_path, old_content, new_content)

题目二：用函数编写tail工具

import time
def tail():
    with open('access.log', mode='rb') as f:
        # 1、将指针跳到文件末尾
        # f.read() # 错误
        f.seek(0, 2)

        while True:
            line = f.readline()
            if len(line) == 0:
                time.sleep(5)
            else:
                print(line.decode('utf-8'), end='')
tail()

题目三：用函数编写登录功能

def login():
    count = 0
    count_1 = 3
    user_name = input('输入账号：').strip()
    with open('db.txt', mode='rt', encoding='utf-8') as f:
        for i in f:  # 定义文本中的账号密码
            info_name, info_pwd = i.strip().split(':')
            if user_name == info_name:
                with open('black.txt', mode='r+t', encoding='utf-8') as f1:
                    for n in f1:
                        # print( user_name,n,end='') # 验证输入账号跟黑名单账号
                        name1 = n.strip()  # 因为文件中每一行默认有个换行'
' 所以要加strip去空格
                        if user_name == name1:
                            print('该账号被锁定')
                            break
                    else:
                        print('
该账号没有被锁定,可以输入密码')
                        while count < 3:
                            print('你还有%s次机会' % (count_1))
                            user_pwd = input('输入密码：')
                            if user_pwd == info_pwd:
                                print('登录成功')
                                break
                            else:
                                print('密码错误')
                                count += 1
                                count_1 -= 1
                        else:
                            print('密码错误过多，该账号已被锁定')
                        with open('black.txt', mode='at+', encoding='utf-8') as f2:
                            f2.write('
%s' % (user_name))
                break
        else:
            print('没有该账号')
login()

题目四：用函数编写注册功能

def creat():
    name = input('注册账号:')
    password = input('注册密码:')
    with open('db.txt', mode='r+t', encoding='utf-8') as f:
        for i in f:
            info_name, info_pwd = i.strip().split(':')
            if name == info_name:
                print('账号已注册')
                break
        else:
            with open('db.txt', mode='at', encoding='utf-8') as n:
                n.write('{}:{}
'.format(name, password))
                print('完成注册')

    user = input('请输入用户名:')
    pwd = input('请输入密码:')
    with open(r'user_info.txt', 'a', encoding='utf-8') as f:
        f.write('{}:{}
'.format(user, pwd))
        print('注册成功')
creat()