How to use Django Password validation in my existing views?

Question

I have an existing django views.py where I have some password, username, and email validation logic applied. However, going forward I need to apply more advanced password validation. for e.g. password length limitation, uppercase sesitivity etc. I have a code written for advanced validation, but I am not able to apply them on my existing views.py. Below is the code from views.py

from django.shortcuts import render, redirect
from django.contrib.auth.models import User
from django.contrib import messages
from . import validator
def register(request):
    if request.method == 'POST':
        first_name = request.POST['first_name']
        last_name = request.POST['last_name']
        email = request.POST['email']
        username = request.POST['username']
        password = request.POST['password', validator.MinimumLengthValidator]
        password2 = request.POST['password2']

        # check if the password match
        if password == password2:

            if User.objects.filter(username=username).exists():
                messages.error(request, 'username already exist')
                return redirect('register')
            else:
                if User.objects.filter(email=email).exists():
                    messages.error(request, 'Registration Failed - Try different email address')
                    return redirect('register')
                else:
                    user = User.objects.create_user(username=username, password=password, email=email,
                                                    first_name=first_name, last_name=last_name)
                    user.save()
                    messages.success(request, 'Registration complete, please proceed to login')
                    return redirect('register')
        else:
            messages.error(request, 'password dose not match')
            return redirect('register')
    else:
        return render(request, 'ACCOUNTS/register.html')

Below is the code for advanced password validation from validate.py

import re    
from django.core.exceptions import ValidationError
from django.utils.translation import ugettext as _    

class MinimumLengthValidator:
    def __init__(self, min_length=8):
        self.min_length = min_length

    def validate(self, password, user=None):
        if len(password) < self.min_length:
            raise ValidationError(
                _("This password must contain at least %(min_length)d characters."),
                code='password_too_short',
                params={'min_length': self.min_length},
            )

    def get_help_text(self):
        return _(
            "Your password must contain at least %(self.min_length)d characters."
            % {'min_length': self.min_length}
        )


class NumberValidator(object):
    def validate(self, password, user=None):
        if not re.findall('\d', password):
            raise ValidationError(
                _("The password must contain at least %(min_digits)d digit(s), 0-9."),
                code='password_no_number',
            )

    def get_help_text(self):
        return _(
            "Your password must contain at least 1 digit, 0-9."
        )


class UppercaseValidator(object):
    def validate(self, password, user=None):
        if not re.findall('[A-Z]', password):
            raise ValidationError(
                _("The password must contain at least 1 uppercase letter, A-Z."),
                code='password_no_upper',
            )

    def get_help_text(self):
        return _(
            "Your password must contain at least 1 uppercase letter, A-Z."
        )

I have tried below steps.

I imported the validator.py in the views.py,and tried to call the module.function inside the password field as below

password = request.POST['password', validator.MinimumLengthValidator]

But that doesn't work. If I am right, I can write a mixin class and call it in my views.py. But I am using function based views. So, I am not sure if I can use mixin. Please suggest how can we achieve the desired result.

New error:

ValidationError at /accounts/register/
['The password must contain at least 1 uppercase letter, A-Z.']
Request Method: POST
Request URL:    http://127.0.0.1:8000/accounts/register/
Django Version: 2.1.5
Exception Type: ValidationError
Exception Value:    
['The password must contain at least 1 uppercase letter, A-Z.']
Exception Location: /root/PycharmProjects/interview/ACCOUNTS/validator.py in validate, line 45
Python Executable:  /root/PycharmProjects/myvenv/bin/python
Python Version: 3.6.7
Python Path:    
['/root/PycharmProjects/interview',
 '/usr/lib/python36.zip',
 '/usr/lib/python3.6',
 '/usr/lib/python3.6/lib-dynload',
 '/root/PycharmProjects/myvenv/lib/python3.6/site-packages']
Server time:    Wed, 6 Feb 2019 07:15:39 +0000

Answer 1

You need to use forms to use those validators cleanly. Although you need to change those as well.

def min_length(password):  # validator
    if not re.findall('\d', password):
        raise ValidationError(
            _("The password must contain at least %(min_digits)d digit(s), 0-9."),
            code='password_no_number',
        )

Then update the form:

# in forms

class UserForm(forms.Form): 
  password = forms.CharField(widget=forms.PasswordInput(),validators=[min_length])

But, if don't want to use django forms, then you need to run those validation manually, for example:

def register(request):
    validators = [MinimumLengthValidator, NumberValidator, UppercaseValidator]
    if request.method == 'POST':
       # some code
       password = request.POST('password')
       try:
           for validator in validators:
                validator().validate(password)
       except ValidationError as e:
           messages.error(request, str(e))
           return redirect('register')