python - 为什么我会收到此 PicklingError？

Question

我正在做一个 Python/Django/Wagtail 项目，我有一些 api 可以返回一些分页的文章。它是这样的:

在网址中:

url(r'^morearticles/', views.get_live_articles),

在 View 中:

def get_live_articles(request):
  context = {'articles': getLiveArticles(request) }
  return render(request, 'app/components/articles-live.html', context, content_type="text/html; charset=utf-8")

getLiveArticles 函数如下所示:

def getLiveArticles(request):

 # Articles
 a = get_articles() #this is getting the articles correctly
 p = Paginator(a, 4)
 page_n = request.GET.get('page')

 try:
     articles = p.page(page_n)
 except Exception, e:
     articles = []

 return articles

然而，当我访问 api 端点时，我得到了这个:

    Traceback (most recent call last):
  File "/Users/john/.virtualenvs/upgrade/lib/python2.7/site-packages/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "/Users/john/.virtualenvs/upgrade/lib/python2.7/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response
    response = self._get_response(request)
  File "/Users/john/.virtualenvs/upgrade/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/Users/john/.virtualenvs/upgrade/lib/python2.7/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/john/app/app/views.py", line 90, in get_live_articles
    context = {'articles': getLiveArticles(request) }
  File "/Users/john/.virtualenvs/upgrade/lib/python2.7/site-packages/cache_utils/decorators.py", line 48, in wrapper
    cache.set(key, value, timeout, **backend_kwargs)
  File "/Users/john/.virtualenvs/upgrade/lib/python2.7/site-packages/django/core/cache/backends/locmem.py", line 75, in set
    pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
PicklingError: Can't pickle <class 'wagtail.wagtailcore.blocks.base.RichTextBlockMeta'>: attribute lookup wagtail.wagtailcore.blocks.base.RichTextBlockMeta failed

我以前遇到过 Pickling 错误，但一直不太明白它是怎么回事。知道是什么原因造成的吗？

如果我应该提供更多信息，请告诉我。调试后我认为问题必须包含在这些代码块中，但我可能错了。

编辑:对象的一个​​字段最近已变成包含主要内容的 StreamField 对象。这可能有什么关系吗？

Answer 1

我认为这是缓存相关的(最近有同样的问题)，其中一些对象不能被 pickle 用于缓存，并且你已经确认你正在使用缓存。所以禁用缓存将解决问题。

我建议使用 pickle 兼容的对象类型。另一方面在Python documentation有一些关于如何实现/自定义 pickling/unpickling 逻辑的指南。