How do I forcefully clean a field and redisplay it in Django?
If, after you've cleaned your form with is_valid(), you render that cleaned form with your view, rather than redirect to a new page, you'll see the cleaned data in your page. 
(If you wanted the user to see this cleaned data and then properly submit it, you could use a hidden field to track whether the form data has already been cleaned, but this isn't without complications...)
How can I clean the data in a form and have the cleaned data  redisplayed instead of the submitted data?
There are several fields in my form, and every time the user submits it, it should be redisplayed with the values the user entered. However, some of the fields I would like to clean and update for the user. More specifically, I have a field FriendlyIntegerField(forms.CharField) in which I override to_python to not only call int(str(value)), but also set any negative number to 0 etc. I do not want to redisplay the form with the invalid data and have the user fix it himself (which is how Django wants me to do it).
I don't have a problem cleaning the data and use it for the rest of my view-function, but how can I update the actual form with this data?
By the way, the form does not reflect a structure in my data model, and so inherits from Form, not ModelForm.
Edit:
My Field (in a stripped down version) looks like this:

class FriendlyIntegerField(forms.CharField):
    def to_python(self, value):
        try:
            return str(int(str(value).replace(' ','')))
        except:
            raise forms.ValidationError('some error msg')

My Form (in a stripped down version) looks like this:

class SearchForm(forms.Form):
    price_from = FriendlyIntegerField()
    price_to = FriendlyIntegerField() 

And my view:

def search(request, key):
    if request.method == 'POST':
        form = SearchForm(request.REQUEST)
        if not form.is_valid():
            print "Form not valid"
    else:
        form = SearchForm()
    return render_to_response('path_to_template', {'form' : form}