django中嵌套的try-except实例

# 因为此时为yaml模板，而且只抓取node port，所以这样处理效率快
content_dict = parse_yaml(content.replace("{{", "").replace("}}", ""))
if 'service' in content_dict.keys():
  # 记录本次yaml里所有的node_port，并更新到数据库
  now_app_list = []
  for service_item in content_dict['service']:
    for port_item in service_item['port']:
      if 'nodePort' in port_item.keys():
        node_port = int(port_item['nodePort'])
        if 30000 <= node_port <= 32000:
          # 这里判断比较复杂，如果端口有，而且app相同，不更新。如果端口有，app不一样，报冲突。如果端口没有，可插入。
          now_app_list.append(node_port)
          try:
            AppPort.objects.get(node_port=node_port, app=app)
            pass
          except AppPort.DoesNotExist:
            try:
              AppPort.objects.get(node_port=node_port)
              messages.info(self.request, 'nodeport{}端口冲突！'.format(node_port))
              return HttpResponseRedirect(reverse_lazy("app:yaml_edit", kwargs=self.kwargs))
            except AppPort.DoesNotExist:
              name = '{}-{}'.format(app.name, node_port)
              AppPort.objects.create(
                name=name,
                app=app,
                node_port=node_port
              )
        else:
          messages.info(self.request, 'nodeport{}端口不在指定范围内(30000-~32000)！'.format(node_port))
          return HttpResponseRedirect(reverse_lazy("app:yaml_edit", kwargs=self.kwargs))
  # 取出AppPort里所有此app的node_port，多余的要清除。
  all_app_list = AppPort.objects.filter(app=app).values_list('node_port', flat=True)
  if all_app_list:
    # 取交集，也就是数据库里多余的端口列表
    diff_list = [x for x in all_app_list if x not in now_app_list]
    if diff_list:
      AppPort.objects.filter(node_port__in=diff_list).delete()

try:
  self.check_quota_enough(create_form) # 检查配额
except Exception as e:
  self.object.state = 5
  self.object.save()
  raise e

# 在dispatch方法上增加装饰器，关闭事务
class xxxxxxxx():
 @method_decorator(transaction.non_atomic_requests)
 def dispatch(self, request, *args, **kwargs):
   return super().dispatch(request, *args, **kwargs)
 
 def form_valid(self, form):
 ...
 ...
 try:
   self.check_quota_enough(create_form) # 检查配额
 except Exception as e:
   self.object.state = 5
   self.object.save()
   raise e

class xxxxxxxx():
 
 def form_valid(self, form):
 ...
 ...
 sid = transaction.savepoint() # 定义事务保存点
    try:
      self.check_quota_enough(create_form)
    except QuotaNotEnough as e:
      self.object.state = 5
      self.object.save()
      transaction.savepoint_commit(sid)
      return self.render_to_json_response(result=False, messages=str(e))