TypeError：不受支持的操作數類型

Question

當試圖檢查運輸變量是否爲空（請參閱下文）時，我得到類型錯誤。該字段是使用django設置的貨幣字段...最新的正確方法是檢查它是否爲空。

Traceback (most recent call last): 

    File "core/handlers/base.py", line 111, in get_response 
    response = callback(request, *callback_args, **callback_kwargs) 

File "contrib/admin/options.py", line 307, in wrapper 
return self.admin_site.admin_view(view)(*args, **kwargs) 

File "utils/decorators.py", line 93, in _wrapped_view 
response = view_func(request, *args, **kwargs) 

File "views/decorators/cache.py", line 79, in _wrapped_view_func 
response = view_func(request, *args, **kwargs) 

File "contrib/admin/sites.py", line 197, in inner 
return view(request, *args, **kwargs) 

File "admin.py", line 21, in changelist_view 
return super(HeldOrderAdmin,self).changelist_view(request, extra_context=extra_context) 

File "utils/decorators.py", line 28, in _wrapper 
return bound_func(*args, **kwargs) 

File "utils/decorators.py", line 93, in _wrapped_view 
response = view_func(request, *args, **kwargs) 

File "utils/decorators.py", line 24, in bound_func 
return func(self, *args2, **kwargs2) 

File "contrib/admin/options.py", line 1179, in changelist_view 
], context, context_instance=context_instance) 

File "shortcuts/__init__.py", line 20, in render_to_response 
return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_kwargs) 

File "template/loader.py", line 188, in render_to_string 
return t.render(context_instance) 

File "template/base.py", line 123, in render 
return self._render(context) 

File "template/base.py", line 117, in _render 
return self.nodelist.render(context) 

File "template/base.py", line 744, in render 
bits.append(self.render_node(node, context)) 

File "template/base.py", line 757, in render_node 
return node.render(context) 

File "template/loader_tags.py", line 127, in render 
return compiled_parent._render(context) 

File "template/base.py", line 117, in _render 
return self.nodelist.render(context) 

File "template/base.py", line 744, in render 
bits.append(self.render_node(node, context)) 

File "template/base.py", line 757, in render_node 
return node.render(context) 

File "template/loader_tags.py", line 127, in render 
return compiled_parent._render(context) 

File "template/base.py", line 117, in _render 
return self.nodelist.render(context) 

File "template/base.py", line 744, in render 
bits.append(self.render_node(node, context)) 

File "template/base.py", line 757, in render_node 
return node.render(context) 

File "template/loader_tags.py", line 127, in render 
return compiled_parent._render(context) 

File "template/base.py", line 117, in _render 
return self.nodelist.render(context) 

File "template/base.py", line 744, in render 
bits.append(self.render_node(node, context)) 

File "template/base.py", line 757, in render_node 
return node.render(context) 

File "template/loader_tags.py", line 64, in render 
result = block.nodelist.render(context) 

File "template/base.py", line 744, in render 
bits.append(self.render_node(node, context)) 

File "template/base.py", line 757, in render_node 
return node.render(context) 

File "template/loader_tags.py", line 64, in render 
result = block.nodelist.render(context) 

File "template/base.py", line 744, in render 
bits.append(self.render_node(node, context)) 

File "template/base.py", line 757, in render_node 
return node.render(context) 

File "template/base.py", line 921, in render 
dict = func(*args) 

File "contrib/admin/templatetags/admin_list.py", line 232, in result_list 
'results': list(results(cl))} 

File "contrib/admin/templatetags/admin_list.py", line 217, in results 
yield ResultList(None, items_for_result(cl, res, None)) 

File "contrib/admin/templatetags/admin_list.py", line 209, in __init__ 
super(ResultList, self).__init__(*items) 

File "contrib/admin/templatetags/admin_list.py", line 137, in items_for_result 
f, attr, value = lookup_field(field_name, result, cl.model_admin) 

File "contrib/admin/util.py", line 214, in lookup_field 
value = attr(obj) 

File "admin.py", line 50, in total 
return '$%s' % (obj.order.total(),) 

File "models.py", line 234, in total 
if item.total is not None: 

File "models.py", line 356, in total 
shipping = 0 

TypeError: unsupported operand type(s) for +: 'NoneType' and 'Decimal' 

Answer 1

total += item.total也許這段代碼是錯誤的。檢查total或item.total是NoneType

因爲你的錯誤是TypeError: unsupported operand type(s) for +: 'NoneType' and 'Decimal'，所以由運營商+