from django.forms.models import model_to_dict
from copy import copy

def UPOST(post, obj):
    """Updates request's POST dictionary with values from object, for update purposes"""
post = copy(post)
for k, v in model_to_dict(obj).items():
    if k not in post:
        post[k] = v
return post
Django обновляет одно поле, используя ModelForm