src_file=input('源文件路径>>: ').strip()
dst_file=input('请输入保存文件路径>>: ').strip()
with open(r'{}'.format(src_file),mode='rt',encoding='utf-8') as f1,\
    open(r'{}'.format(dst_file),mode='wt',encoding='utf-8') as f2:
    res=f1.read()
    f2.write(res)

inp_username=input('your name>>: ').strip()
inp_password=input('your password>>: ').strip()

# 验证
with open('user.txt',mode='rt',encoding='utf-8') as f:
    for line in f:
       username,password=line.strip().split(':')
        if inp_username == username and inp_password == password:
            print('login successfull')
            break
    else:
        print('账号或密码错误')

name=input('your name>>: ')
pwd=input('your name>>: ')
with open('db.txt',mode='at',encoding='utf-8') as f:
    f.write('{}:{}\n'.format(name,pwd))