这段代码明明是对的，为什么会username不匹配

Question

with open('b.txt',mode='rt',encoding='utf-8') as f:
    res = f.read()
    username,password = res.split(':')


inp_username = input('please input your username:').strip()

inp_password = input('please input your password:')


if inp_username == username.strip() and inp_password == password:
    print('login successful')
elif inp_username == username.strip() and inp_password != password:
    print('username or password error1')
elif inp_username != username.strip() and inp_password == password:
    print('username or password error2')
print(username,password,inp_username,inp_password)

please input your username:fang
please input your password:123
username or password error2
fang 123 fang 123

Process finished with exit code 0
 

Answer 1

我知道问题的所在了，从txt文件中取出来的时候，变量前自动加了个'\ufef'的前缀，我搜了搜是BOM的问题，我也不大明白其中的原理，不过将从txt文件中取出来的编码格式换成utf-8-sig就好了，不过大佬能细细讲一下其中的原理吗