Validate Django user max length object against database

user_object_max_length_validation.py

from django.contrib.auth.models import User
from django.db.models.fields import FieldDoesNotExist

# Used for user import feature.
# There's no form validation; so we validate max_length this way.

# loop through user properties; truncate at max_length
for key, value in user.__dict__.items():
    max_length = None
    try:
        max_length = User._meta.get_field_by_name(key)[0].max_length
    except FieldDoesNotExist as e:
        if max_length:  # truncate per max_length field attribute
            setattr(user, key, value[:max_length])