Python 如何在文本字段中显示初始值？

我加载表单。我需要在文本字段

city

中显示初始值

型号：

class City(models.Model):       
    city = models.CharField(
        max_length=40,  blank=True,
    )           

class UserProfile(User):            
    family = models.CharField(
        'Фамилия',  max_length=30,  blank=True, null=True,
    )
    city = models.ForeignKey(
        City, verbose_name='Город', max_length=50,  blank=True, null=True,
    )

表格：

class PersonalDataForm(forms.ModelForm):
    city = forms.CharField(
        label='Город',
        required=False,
    )   

    class Meta:
        model = UserProfile
        fields = (
            'family', 
        )       

    def save(self):
        obj = super(PersonalDataForm, self).save(commit=False)
        city_name = self.cleaned_data.get('city', None).strip()                         

        if city_name:
            if City.objects.filter(city=city_name).exists():
                obj.city = City.objects.get(city=city_name)
            else:
                rec = City(city=city_name)
                rec.save()
                obj.city = rec  
        else:
            obj.city = None             

        return obj.save()

观点：

def personal_data_page(request):
    entry_user_profile = UserProfile.objects.get(user_ptr_id=request.user.id)
    form = PersonalDataForm(instance=entry_user_profile)

    if request.method == 'POST':
        form = PersonalDataForm(request.POST, instance=entry_user_profile)
        if form.is_valid(): 
            form.save()         
            return HttpResponseRedirect('/userprofile/personal_data_page_changed/')             

    t = loader.get_template('personal_data_page.html')
    c = RequestContext(request, {
        'form': form,
    }, [custom_proc])
    return HttpResponse(t.render(c)) 

template.html：

{{ family.city }}
{{ form.city }}

---

问题是加载表单时，表单字段“city”为空。但它必须包含表中的值（表中充满值​​)

如果使用此模式，初始值应可见：

if request.method=='POST':
    data=request.POST
else:
    data=None

form=MyForm(data, initial=...)

if (not data is None) and form.is_valid():
    form.save()
    return django.http.HttpResponseRedirect(...)
return HttpResponse(render(...))