Why authenticate() return None for inactive users?

问题

I have CustomUser like following :

        class CustomUser(AbstractBaseUser, PermissionsMixin):
            email = models.EmailField(max_length=100, unique=True)
            username = models.CharField(max_length=20, unique=True)
            is_active = models.BooleanField(default=False)
            is_staff = models.BooleanField(default=False)
            ...

which is active default=False After user registration automatically handle UserLogin def which is :

        def UserLogin(request):
            if request.POST:
                username = request.POST['username']
                user = authenticate(username=username, password=request.POST['password'])
                print('user :', user)  # which is print None if user inactive 
                if user is not None:
                    print('is user active:', user.is_active)   # should print True or False  
                    if user.is_active:
                        login(request, user)
                        ... 
                    else:  # handle user inactive
                        ...
                else:  # for None user 
                   ...

I still trying understanding why authenticate return None for inactive users ?

After searching I found smilier issue user.is_authenticated always returns False for inactive users on template But didn't find an answer for my situation

回答1:

Firstly, note that Django comes with a login view and authentication form which display suitable error messages when inactive users try to log in. If you use them, then you probably don't have to change the behaviour for authenticate().

Since Django 1.10, the default ModelBackend authentication backend does not allow users with is_active = False to log in.

If you want to allow inactive users to log in, then you can use the AllowAllUsersModelBackend backend.

AUTHENTICATION_BACKENDS = ['django.contrib.auth.backends.AllowAllUsersModelBackend']

See the is_active docs for more info,

来源：https://stackoverflow.com/questions/49553511/why-authenticate-return-none-for-inactive-users