怎么用foreignkey 实现Django下拉选择框

from django.shortcuts import render
from django.views.generic import View


def addReport(View):
    form_class = EnteringForm()
    template_name = 'report_template.html'

    def post(self, request, *args, **kwargs):
        form = self.form_class(request.POST)
        if form.is_valid():
            report_tuple = ReportModel(
                user=request.user.username,
                school=form_context.cleaned_data['school'],
                grade=form_context.cleaned_data['grade'],
                home_location=form_context.cleaned_data['home_location'],
            )
            report_tuple.save()
            form = EnteringForm()
        else:
            return HttpResponse(form_context['user'].errors)
        return render(request, self.template_name, {'form': form})

def  addReport(request):
form_context = EnteringForm()
if request.method == 'POST':
    form_context= EnteringForm( request.POST )
    # 这里是增添数据部分
    if form_context.is_valid():
        report_tuple = ReportModel(
            user= request.user.username,
            school= form_context .cleaned_data['school'],
            grade= form_context .cleaned_data['grade'],
            home_location= form_context .cleaned_data['home_location'],
        )
        report_tuple .save()
        form_context= EnteringForm()
    else:
        return HttpResponse(form_context ['user'].errors)
return render_to_response('report_template.html', RequestContext(request,
                                                           locals(),
                                                           )
                          )

class AccountItemForm(forms.Form):
    item_type_choice = ((1, "支出"), (0, "收入"),)
    datetime = forms.DateTimeField(label="帐目日期")
    detail = forms.CharField(widget=forms.Textarea, label="帐目明细", max_length=65535)
    money = forms.DecimalField(label="单位金额", min_value=0.01, max_digits=10, decimal_places=2)
    quantity = forms.IntegerField(label="数量", min_value=1)
    account_type = forms.ChoiceField(label="帐目类型", required=True, widget=forms.Select, choices=(),)
    item_type = forms.ChoiceField(
        label="帐目操作",
        required=True,
        widget=forms.RadioSelect(renderer=RadioCustomRenderer),
        choices=item_type_choice,
        initial='1')

    def set_item_type_choices(self, request):
       //blablabla

def account_create(request):
    next_path = '/accountbook'
    if not request.user.is_authenticated():// 提前判断用户是否合法
        return message_page(request, '访问错误', '未登录，不能新建帐目。', nextpath=next_path)
    items = Account_item.objects.filter(
        user=request.user).values('detail').distinct()
    if request.method == 'POST':
        item_form = AccountItemForm(request.POST)
        item_form.set_item_type_choices(request)
        if item_form.is_valid():
            account_type_id = int(item_form.cleaned_data['account_type'])
            account_type = None
            item_type = item_form.cleaned_data['item_type']
            money = Decimal(item_form.cleaned_data['money'])
            if int(item_type) is 1:
                money = -money
            if not account_type_id is 0:
                try:
                    account_type = Account_type.objects.get(id=account_type_id)
                    # if not account_type.owner and not account_type.owner is request.user:
                    #    account_type = None
                except Account_type.DoesNotExist:
                    account_type = None
            new_item = Account_item(
                user=request.user, //看这里，save的时候直接赋值进去了
                detail=item_form.cleaned_data['detail'],
                datetime=item_form.cleaned_data['datetime'],
                money=money,
                quantity=item_form.cleaned_data['quantity'],
                account_type=account_type)
            new_item.save()
            return HttpResponseRedirect(next_path)

def is_valid(self):
    """
    Returns True if the form has no errors. Otherwise, False. If errors are
    being ignored, returns False.
    """
    return self.is_bound and not self.errors

            type_form = AccountTypeForm(
                initial={
                    'title': account_type.title,
                    'detail': account_type.detail,
                }
            )