Django不能连接＆＃39; str＆＃39;和＆＃39; NoneType＆＃39;对象

Question

我尝试为{{ event.reports_dump | safe }}来自此行tmpls.append("<span>"+event.human_date_range()+"</span>")生成事件模型的报告时遇到此错误，它使用创建的自定义函数来制作人类可读文本。

我尝试通过首先返回字符串＆＃34;无＆＃34;来解决问题。而不是什么

def human_date_range(self):
    ...
    if not (starts and ends):
        #from return to return "None"
        return "None"

但迁移并重新启动服务器后错误仍然存​​在。我可以告诉更改已从错误日志生效，所以我覆盖了整个函数，但它仍然返回相同的错误

def human_date_range(self):
    ...
    return "None"
    if not (starts and ends):
        #from return to return "None"
        return "None"

需要一些调试帮助。

我已经粘贴了错误日志和模型

class Event(BaseItemModel, AdminURLMixin):
    venue = models.ForeignKey(Venue)
    categories = TreeManyToManyField(Category)

    parent = models.ForeignKey('Event', blank=True, verbose_name='Parent Event', null=True,)

    contact_person = models.CharField(max_length=255, blank=True,)
    contact_email = models.EmailField(max_length=255, blank=True, help_text='Only one valid email address allowed')
    contact_phone = models.CharField(max_length=255, blank=True,)
    contact_website = models.URLField(max_length=255, blank=True, help_text='Only one valid web address allowed. Must include http:// or https://')
    contact_address = models.TextField(blank=True,)

    free = models.BooleanField(default=False)
    taxi = models.NullBooleanField(default=None)
    jkia_ad = models.NullBooleanField(default=None)
    cost = models.PositiveIntegerField(blank=True, null=True, verbose_name="Cost in KES", default=0, help_text='Only numbers allowed, if price is not in KES convert the amount to KES and write the Currency and Cost in Cost Description')
    cost_desc = models.TextField(blank=True, verbose_name='Cost description', help_text='If several prices available write them here using the regular price in Cost')

    artist = models.TextField(blank=True,)
    event_ticket = models.IntegerField(blank=True, null=True)

    num_days = models.IntegerField(default=0, editable=False, db_index=True,)

    old_dates = models.TextField(blank=True, editable=False,)


    def human_date_range(self):

        starts = self.starts_datetime()
        ends = self.ends_datetime()

        return "None"

        if not (starts and ends):
            return "None"

        if starts.date() == ends.date():
            # February 21st, 10pm
            return starts.strftime('%B ')+humanize.ordinal(int(starts.strftime('%d')))+', '+str(int(starts.strftime('%I')))+starts.strftime('%p').lower()

        elif starts.year == ends.year and starts.month == ends.month:
            # February 21st, 10pm-11pm
            return\
                starts.strftime('%B ')+humanize.ordinal(int(starts.strftime('%d')))+', '+\
                str(int(starts.strftime('%I')))+starts.strftime('%p').lower()+' - '+str(int(ends.strftime('%I')))+ends.strftime('%p').lower()

        elif starts.year == ends.year:
            # February 21st - March 23rd, 10pm-11pm
            return\
                starts.strftime('%B ')+humanize.ordinal(int(starts.strftime('%d')))+' - '+ends.strftime('%B ')+humanize.ordinal(int(ends.strftime('%d')))+', '+\
                str(int(starts.strftime('%I')))+starts.strftime('%p').lower()+' - '+str(int(ends.strftime('%I')))+ends.strftime('%p').lower()

        else:
            # February 21st 2013 - March 4th 2014, 10pm-11pm
            return starts.strftime('%B ')+humanize.ordinal(int(starts.strftime('%d')))+starts.strftime('  %Y')+' - '+ends.strftime('%B ')+humanize.ordinal(int(ends.strftime('%d')))+ends.strftime('  %Y')+', '+\
            str(int(starts.strftime('%I')))+starts.strftime('%p').lower()+' - '+str(int(ends.strftime('%I')))+ends.strftime('%p').lower()

错误日志

Environment:

Request Method: GET
Request URL: http://stage.kenyabuzz.com/admin/reports/events/2015-12-8-0-0/2015-12-14-0-0/

Django Version: 1.7.10
Python Version: 2.7.5


Template error:
In template /home/kbuzz/webapps/kenyabuzz/kb/reports/templates/reports/report.html, error at line 71
   cannot concatenate 'str' and 'NoneType' objects
   61 : 
   62 :       <div>
   63 :         {% for event in stat.v %}
   64 :         
   65 :         <div class='event'>
   66 : 
   67 :         {% if event.title %}
   68 :         <span class='bold'>{{ event.title }}: </span>
   69 :         {% endif %}
   70 : 
   71 :          {{ event.reports_dump | safe }} 
   72 : 
   73 :         {% if event.description %}
   74 :         <span>{{ event.description }}</span>
   75 :         {% endif %}
   76 : 
   77 :         </div>
   78 : 
   79 :         {% endfor %}
   80 : 
   81 :       </div>


Traceback:
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/core/handlers/base.py" in get_response
  111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/contrib/auth/decorators.py" in _wrapped_view
  21.                 return view_func(request, *args, **kwargs)
File "/home/kbuzz/webapps/kenyabuzz/kb/reports/views.py" in events
  205.         RequestContext(request, {})
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/shortcuts.py" in render_to_response
  25.     return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_kwargs)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/loader.py" in render_to_string
  178.         return t.render(context_instance)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in render
  148.             return self._render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in _render
  142.         return self.nodelist.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in render
  844.                 bit = self.render_node(node, context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/debug.py" in render_node
  80.             return node.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/loader_tags.py" in render
  126.         return compiled_parent._render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in _render
  142.         return self.nodelist.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in render
  844.                 bit = self.render_node(node, context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/debug.py" in render_node
  80.             return node.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/loader_tags.py" in render
  126.         return compiled_parent._render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in _render
  142.         return self.nodelist.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in render
  844.                 bit = self.render_node(node, context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/debug.py" in render_node
  80.             return node.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/loader_tags.py" in render
  65.                 result = block.nodelist.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in render
  844.                 bit = self.render_node(node, context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/debug.py" in render_node
  80.             return node.render(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/defaulttags.py" in render
  201.                             nodelist.append(node.render(context))
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/defaulttags.py" in render
  201.                             nodelist.append(node.render(context))
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/debug.py" in render
  90.             output = self.filter_expression.resolve(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in resolve
  596.                 obj = self.var.resolve(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in resolve
  734.             value = self._resolve_lookup(context)
File "/home/kbuzz/webapps/kenyabuzz/lib/python2.7/Django-1.7.10-py2.7.egg/django/template/base.py" in _resolve_lookup
  788.                             current = current()
File "/home/kbuzz/webapps/kenyabuzz/kb/events/models.py" in reports_dump
  175.         tmpls.append("<span>"+event.human_date_range()+"</span>")

Exception Type: TypeError at /admin/reports/events/2015-12-8-0-0/2015-12-14-0-0/
Exception Value: cannot concatenate 'str' and 'NoneType' objects

Answer 1

你最好使用字符串插值，它可以处理这样的事情。

tmpls.append("<span>{}</span>".format(event.human_date_range()))