How can I get the value of a database field by means of a model in Django?

Good afternoon friends of stackoverflow.

I have the following question as to how I can obtain the value of a field by means of a query in a model of a database please.

Here is the code.

Views.py

class UserFormView(View):
form_class = UserForm
template_name = "registration/registration_form.html"

def get(self, request):
    form = self.form_class(None)
    return render(request, self.template_name, {'form': form})

#process form data
def post(self, request):
    form = self.form_class(request.POST)

    if form.is_valid():
        user = form.save(commit=False)
        #cleaned (normalized) data
        username = form.cleaned_data['username']
        password = form.cleaned_data['password']
        email = form.cleaned_data['email']
        user.set_password(password)
        user.save()
        #Quiero obtener el password segun el username
        user_password = User.objects.get(username=username)
        validate_email(username, user_password, email)
        #returns User objects if credentials are correct
        user = authenticate(username=username, password=password)
        if user is not None:
            if user.is_active:
                auth_login(request, user)
                return redirect('/')
    return render(request, self.template_name, {'form': form})

Models.py

    from django.db import models
from django.db.models.signals import post_save



class User(models.Model):
    username = models.CharField(max_length=32, null=False, blank=False)
    name = models.CharField(max_length=20, null=False, blank=False)
    lastname = models.CharField(max_length=20, null=False, blank=False)
    email = models.EmailField(max_length=64, null=False, blank=False)
    password = models.CharField(max_length=128, null=False, blank=False)
    password_token = models.CharField(max_length=64)
    created_date = models.DateTimeField(auto_now=True)