如何使用表单登录用户？

forms.py:

forms.py：

from django import forms
from django.contrib.auth import authenticate, get_user_model
from django.contrib.auth.models import User
from django.forms import ModelForm
from django.utils.text import capfirst
from .models import Classname, Sectionname, Teachername, Attendancename

class AuthenticationForm(forms.Form):
    username = forms.CharField(max_length=20)
    password = forms.CharField(widget=forms.PasswordInput)
    error_messages = {
        'invalid_login': ("Please enter a correct %(username)s and password."
                          "Note that both fields may be case-sensitive."),
        'inactive': ("This account is inactive"),
    }

    def clean(self):
        username = self.cleaned_data.get('username')
        password = self.cleaned_data.get('password')

        if username and password:
            self.user_cache = authenticate(username=username, password=password)

            if self.user_cache is None:
                raise forms.ValidationError(
                    self.error_messages['invalid_login'],
                    code='invalid_login',
                )
            else:
                self.confirm_login_allowed(self.user_cache)

        return self.cleaned_data

    def confirm_login_allowed(self, user):
        if user.is_active:
            login(self.user)   /** It raises error here... **/
        else:
            raise forms.ValidationError(
                self.error_messages['inactive'],
                code='inactive',
                )

    def get_user_id(self):
        if self.user_cache:
            return self.user_cache.id
        return None

    def get_user(self):
        return self.user_cache
from django import form