Introduction

As the Django documentation says: "A validator is a callable that takes a value and raises a ValidationError if it doesn’t meet some criteria. Validators can be useful for reusing validation logic between different types of fields."

Yes, you can make your own validator. In this example, I am going to create a password validator that will check if the given password contains at least one letter.

To create a custom validator, create a file called validators.py within one of your Django applications.

# validators.py

from django.core.exceptions import ValidationError


class ContainsLetterValidator:
    def validate(self, password, user=None):
        if not any(char.isalpha() for char in password):
            raise ValidationError(
                'The password must contain at least one letter',
                code='password_no_letters'
            )

    def get_help_text(self):
        return 'Your password must contain at least one upper or lower case letter.'

Once you have created the validator, add it to your settings.py file inside the AUTH_PASSWORD_VALIDATORS dictionary.

# settings.py


AUTH_PASSWORD_VALIDATORS = [
    {
        "NAME": "django.contrib.auth.password_validation.NumericPasswordValidator",
        "NAME": "app.validators.ContainsLetterValidator",
    },
]

The validator is now used to validate the creation of a password.

• official Django documentation about validators