Function get_default_username

django/contrib/auth/management/__init__.py:246–292

Try to determine the current system user's username to use as a default. :param check_db: If ``True``, requires that the username does not match an existing ``auth.User`` (otherwise returns an empty string). :param database: The database where the unique check will be performed

(check_db=True, database=DEFAULT_DB_ALIAS)

def get_default_username(check_db=True, database=DEFAULT_DB_ALIAS):
    """
    Try to determine the current system user's username to use as a default.

    :param check_db: If ``True``, requires that the username does not match an
        existing ``auth.User`` (otherwise returns an empty string).
    :param database: The database where the unique check will be performed.
    :returns: The username, or an empty string if no username can be
        determined or the suggested username is already taken.
    """
    # This file is used in apps.py, it should not trigger models import.
    from django.contrib.auth import models as auth_app

    # If the User model has been swapped out, we can't make any assumptions
    # about the default user name.
    if auth_app.User._meta.swapped:
        return ""

    default_username = get_system_username()
    try:
        default_username = (
            unicodedata.normalize("NFKD", default_username)
            .encode("ascii", "ignore")
            .decode("ascii")
            .replace(" ", "")
            .lower()
        )
    except UnicodeDecodeError:
        return ""

    # Run the username validator
    try:
        auth_app.User._meta.get_field("username").run_validators(default_username)
    except exceptions.ValidationError:
        return ""

    # Don't return the default username if it is already taken.
    if check_db and default_username:
        try:
            auth_app.User._default_manager.db_manager(database).get(
                username=default_username,
            )
        except auth_app.User.DoesNotExist:
            pass
        else:
            return ""
    return default_username