Problem with Django forms and cache control

I'm populating the choices of a form choicefield in django, it's a year select field. I get the years from the database and put them in a list of tuples in the field. My code looks like this

def get_years():
    choices = []
    years = []
    for poll in Poll.objects.all().order_by('created'):
        y开发者_Python百科ears.append(poll.created.year)
    for year in list(set(years)):
        choices.append((year, year))
    return choices

and my form field looks like this

year = forms.ChoiceField(choices=get_years())

The problem is that when I see it in the browser, the year list is fine according to the database, but when I change some date in database, the year select list doesn't update. I've tried width @cache_control(no_cache=True) decorator, but doesn't work. Any ideas?

Thanks in advance!

Update the years when you initialize a form instance.

def __init__(self, *args, **kwargs):
   super(MyForm, self).__init__(*args, **kwargs)
   self.fields['year'].choices = self.get_years()