with open('c.txt',mode='rt',encoding='utf-8') as f:
   print('第一次读'.center(50,'*'))
   res=f.read() # 把所有内容从硬盘读入内存
   print(res)
 with open('c.txt', mode='rt', encoding='utf-8') as f:
   print('第二次读'.center(50,'*'))
   res1=f.read()
   print(res1)

 inp_username=input('your name: ').strip()
 inp_password=input('your password: ').strip()
 with open('user.txt',mode='rt',encoding='utf-8') as f:
   for line in f:
     # print(line,end='') # egon:123\n
     username,password=line.strip().split(':') #压缩赋值，取出文件中的用户名密码
     if inp_username == username and inp_password == password:
       print('login successfull')
       break
   else:
     print('账号或密码错误')

with open('d.txt',mode='wt',encoding='utf-8') as f:
# f.read() # 报错，不可读
# f.write('擦勒\n') 
# 强调1：
# 在以w模式打开文件没有关闭的情况下，连续写入，新的内容总是跟在旧的之后
# with open('d.txt',mode='wt',encoding='utf-8') as f:
# f.write('擦勒1\n')
# f.write('擦勒2\n')
# f.write('擦勒3\n')
# 强调2：
# 如果重新以w模式打开文件，则会清空文件内容
# with open('d.txt',mode='wt',encoding='utf-8') as f:
# f.write('擦勒1\n')
# with open('d.txt',mode='wt',encoding='utf-8') as f:
# f.write('擦勒2\n')
# with open('d.txt',mode='wt',encoding='utf-8') as f:
# f.write('擦勒3\n')

# src_file=input('源文件路径: ').strip()
# dst_file=input('目标文件路径: ').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)

with open('e.txt',mode='at',encoding='utf-8') as f:
   # f.read() # 报错，不能读
   f.write('1\n')
   f.write('2\n')
   f.write('3\n')

 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))