[python] Django: Model Form "object has no attribute 'cleaned_data'"

I am trying to make a search form for one of my classes. The model of the form is:

from django import forms
from django.forms import CharField, ModelMultipleChoiceField, ModelChoiceField
from books.models import Book, Author, Category

class SearchForm(forms.ModelForm):
    authors = ModelMultipleChoiceField(queryset=Author.objects.all(),required=False)    
    category = ModelChoiceField (queryset=Category.objects.all(),required=False)
    class Meta:
        model = Book
        fields = ["title"]

And the view I'm using is:

from django.shortcuts import render_to_response, redirect, get_object_or_404
from django.template import RequestContext
from books.models import Book,Author
from books.forms import BookForm, SearchForm
from users.models import User

def search_book(request):
    if request.method == "POST":
        form = SearchForm(request.POST)
        if form.is_valid():
            form = SearchForm(request.POST)
            stitle = form.cleaned_data['title']
            sauthor = form.cleaned_data['author']
            scategory = form.cleaned_data['category']
    else:
        form = SearchForm()
    return render_to_response("books/create.html", {
        "form": form,
    }, context_instance=RequestContext(request))

The form shows up fine, but when I submit it I get an error: 'SearchForm' object has no attribute 'cleaned_data'

I'm not sure what's going on, can someone help me out? Thanks!

I would write the code like this:

def search_book(request):
    form = SearchForm(request.POST or None)
    if request.method == "POST" and form.is_valid():
        stitle = form.cleaned_data['title']
        sauthor = form.cleaned_data['author']
        scategory = form.cleaned_data['category']
        return HttpResponseRedirect('/thanks/')
    return render_to_response("books/create.html", {
        "form": form,
    }, context_instance=RequestContext(request))

Pretty much like the documentation.

At times, if we forget the

return self.cleaned_data 

in the clean function of django forms, we will not have any data though the form.is_valid() will return True.