[Django]-How to make email field unique in model User from contrib.auth in Django

Caution:
The code below was written for an older version of Django (before Custom
User Models were introduced). It contains a race condition, and
should only be used with a Transaction Isolation Level of SERIALIZABLE
and request-scoped transactions.

Your code won’t work, as the attributes of field instances are read-only. I fear it might be a wee bit more complicated than you’re thinking.

If you’ll only ever create User instances with a form, you can define a custom ModelForm that enforces this behavior:

from django import forms
from django.contrib.auth.models import User

class UserForm(forms.ModelForm):
    class Meta:
        model = User

    def clean_email(self):
        email = self.cleaned_data.get('email')
        username = self.cleaned_data.get('username')
        if email and User.objects.filter(email=email).exclude(username=username).exists():
            raise forms.ValidationError(u'Email addresses must be unique.')
        return email

Then just use this form wherever you need to create a new user.

BTW, you can use Model._meta.get_field('field_name') to get fields by name, rather than by position. So for example:

# The following lines are equivalent
User._meta.fields[4]
User._meta.get_field('email')

UPDATE

The Django documentation recommends you use the clean method for all validation that spans multiple form fields, because it’s called after all the <FIELD>.clean and <FIELD>_clean methods. This means that you can (mostly) rely on the field’s value being present in cleaned_data from within clean.

Since the form fields are validated in the order they’re declared, I think it’s okay to occasionally place multi-field validation in a <FIELD>_clean method, so long as the field in question appears after all other fields it depends on. I do this so any validation errors are associated with the field itself, rather than with the form.

What about using unique_together in a “different” way? So far it works for me.

class User(AbstractUser):
    ...
    class Meta(object):
        unique_together = ('email',)

Simply use below code in models.py of any app

from django.contrib.auth.models import User
User._meta.get_field('email')._unique = True

In settings module:

# Fix: username length is too small,email must be unique
from django.contrib.auth.models import User, models
User._meta.local_fields[1].__dict__['max_length'] = 75
User._meta.local_fields[4].__dict__['_unique'] = True

Your form should look something like this.

def clean_email(self):
    email = self.cleaned_data.get('email')
    username = self.cleaned_data.get('username')
    print User.objects.filter(email=email).count()
    if email and User.objects.filter(email=email).count() > 0:
        raise forms.ValidationError(u'This email address is already registered.')
    return email

To ensure a User, no matter where, be saved with a unique email, add this to your models:

@receiver(pre_save, sender=User)
def User_pre_save(sender, **kwargs):
    email = kwargs['instance'].email
    username = kwargs['instance'].username

    if not email: raise ValidationError("email required")
    if sender.objects.filter(email=email).exclude(username=username).count(): raise ValidationError("email needs to be unique")

Note that this ensures non-blank email too. However, this doesn’t do forms validation as would be appropriated, just raises an exception.

Django has a Full Example on its documentation on how to substitute and use a Custom User Model, so you can add fields and use email as username.

One possible way to do this is to have a pre-save hook on the User object and reject the save of the email already exists in the table.

This method won’t make email field unique at the database level, but it’s worth trying.

Use a custom validator:

from django.core.exceptions import ValidationError
from django.contrib.auth.models import User

def validate_email_unique(value):
    exists = User.objects.filter(email=value)
    if exists:
        raise ValidationError("Email address %s already exists, must be unique" % value)

Then in forms.py:

from django.contrib.auth.models import User
from django.forms import ModelForm
from main.validators import validate_email_unique

class UserForm(ModelForm):
    #....
    email = forms.CharField(required=True, validators=[validate_email_unique])
    #....

I think that the correct answer would assure that uniqueness check was placed inside the database (and not on the django side). Because due to timing and race conditions you might end with duplicate emails in the database despite having for example pre_save that does proper checks.

If you really need this badly I guess you might try following approach:

1. Copy User model to your own app, and change field email to be unique.
2. Register this user model in the admin app (using admin class from django.contrib.auth.admin)
3. Create your own authentication backend that uses your model instead of django one.

Add the below function in any of the models.py file. Then run makemigrations and migrate. Tested on Django1.7

def set_email_as_unique():
    """
    Sets the email field as unique=True in auth.User Model
    """
    email_field = dict([(field.name, field) for field in MyUser._meta.fields])["email"]
    setattr(email_field, '_unique', True)

#this is called here so that attribute can be set at the application load time
set_email_as_unique()

Since version 1.2 (May 11th, 2015) there has been a way to dynamically import any chosen registration form using the settings option REGISTRATION_FORM.

So, one could use something like this:

REGISTRATION_FORM = 'registration.forms.RegistrationFormUniqueEmail'

This is documented here.

And here’s the link to the changelog entry.

Django does not allow direct editing User object but you can add pre_save signal and achieve unique email. for create signals u can follow https://docs.djangoproject.com/en/2.0/ref/signals/. then add the following to your signals.py

 @receiver(pre_save, sender=User)
def check_email(sender,instance,**kwargs):
    try:
        usr = User.objects.get(email=instance.email)
        if usr.username == instance.username:
            pass
        else:
            raise Exception('EmailExists')
    except User.DoesNotExist:
        pass

Add somewhere this:

User._meta.get_field_by_name('email')[0]._unique = True     

and then execute SQL similar to this:

ALTER TABLE auth_user ADD UNIQUE (email);

The first answer here is working for me when I’m creating new users, but it fails when I try to edit a user, since I am excluding the username from the view. Is there a simple edit for this that will make the check independent of the username field?

I also tried including the username field as a hidden field (since I don’t want people to edit it), but that failed too because django was checking for duplicate usernames in the system.

(sorry this is posted as an answer, but I lack the creds to post it as a comment. Not sure I understand Stackoverflow’s logic on that.)

You can use your own custom user model for this purpose. You can use email as username or phone as username , can have more than one attribute.

In your settings.py you need to specify below settings
AUTH_USER_MODEL = ‘myapp.MyUser’.

Here is the link that can help you .
https://docs.djangoproject.com/en/1.8/topics/auth/customizing/#auth-custom-user

from an User inherited model, redefine the attribute correctly. It should work, as is it’s not usefull to have that in django core because it’s simple to do.

I went to \Lib\site-packages\django\contrib\auth\models
and in class AbstractUser(AbstractBaseUser, PermissionsMixin):
I changed email to be:

email = models.EmailField(_('email address'), **unique=True**, blank=True)

With this if you try to register with email address already present in the database you will get message: User with this Email address already exists.