如何得到django中form表單里的復選框（多選框）的值（ MultipleChoiceField ）

直接寫代碼吧

CHECKBOX_CHOICES = (
         ('Value1','Value1'),
         ('Value2','Value2'),
)

class EditProfileForm(ModelForm):
    interest = forms.MultipleChoiceField(required=False, 
                                    widget=CheckboxSelectMultiple(), 
                                    choices=CHECKBOX_CHOICES,)

    def save(self, *args, **kwargs):
        u = self.instance.user
        u.interest = self.cleaned_data['interest']
        u.save()
        profile = super(EditProfileForm, self).save(*args,**kwargs)
        return profile

怎樣得到如下數據呢 

[u'value1', u'value2']

實現

u.interest = u','.join(self.cleaned_data['interest'])