Как изменить значение поля формы Django перед сохранением? ⇐ Python

[Anonymous]

if request.method == 'POST':
userf = UsersModelForm(request.POST)
username = userf.data['username']
password = userf.data['password']
passwordrepeat = userf.data['passwordrepeat']
email = userf.data['email']


Я пробовал это:

tempSalt = bcrypt.gensalt()
password = bcrypt.hashpw(password,tempSalt)
passwordrepeat = bcrypt.hashpw(passwordrepeat,tempSalt)

userf.data['password'] = password
userf.data['passwordrepeat'] = passwordrepeat


Но у меня возникла ошибка. Как я могу изменить значение userf.data['password'] и userf.data['passwordrepeat'] перед сохранением?

Ошибка:

AttributeError at /register

This QueryDict instance is immutable

Request Method: POST
Request URL: http://127.0.0.1:8000/register
Django Version: 1.3.1
Exception Type: AttributeError
Exception Value:

This QueryDict instance is immutable

Exception Location: /usr/local/lib/python2.6/dist-packages/django/http/__init__.py in _assert_mutable, line 359
Python Executable: /usr/bin/python
Python Version: 2.6.6
Python Path:

['/home/user1/djangoblog',
'/usr/lib/python2.6',
'/usr/lib/python2.6/plat-linux2',
'/usr/lib/python2.6/lib-tk',
'/usr/lib/python2.6/lib-old',
'/usr/lib/python2.6/lib-dynload',
'/usr/local/lib/python2.6/dist-packages',
'/usr/lib/python2.6/dist-packages',
'/usr/lib/python2.6/dist-packages/gst-0.10',
'/usr/lib/pymodules/python2.6',
'/usr/lib/pymodules/python2.6/gtk-2.0']


Подробнее здесь: https://stackoverflow.com/questions/892 ... ore-saving