pythondjango问题，和现有的tag取交集后得出来的词怎么添加到文章的tags里?

class Tags(models.Model):

    name = models.CharField(max_length = 36, verbose_name = _(u'标签'))

    slug = models.SlugField(max_length = 50, verbose_name = _(u'标签url'), default = 'tags')

    num = models.PositiveIntegerField(verbose_name = _(u'标签排序'), default = 0)

   

    def __unicode__(self):

        return self.name

   

    class Meta:

        verbose_name_plural = u'标签名字'

       

    def get_absolute_url(self):

        return reverse('info:tags', kwargs = {'slug':self.slug})

class CreateTopicForm(forms.ModelForm):

    tags = forms.ModelMultipleChoiceField(queryset=Tags.objects.all(), widget=forms.CheckboxSelectMultiple(), required=False)

    category = forms.ModelChoiceField(queryset=Category.objects.all(), widget=forms.RadioSelect(), initial={'headline': 'Initial headline'})

    def __init__(self, *args, **kwargs):

        self.user = kwargs.pop('user',None)

        super(CreateTopicForm, self).__init__(*args, **kwargs)

    class Meta:

        model = Topic

        fields = ['title', 'category', 'body', 'tags',]



    def save(self, commit=True):

        inst = super(CreateTopicForm, self).save(commit = False)

        inst.author = self.user

        if commit:

            inst.save()

            self.save_m2m()

        return inst

import jieba

import jieba.posseg as pseg    

pctaglist = ['高兴', '你好', '上海', '抑郁症', '头晕']



@login_required

def create_info(request):

    if request.method == "POST":

        form = CreateTopicForm(request.POST, user=request.user)

        if form.is_valid():

            body = form.cleaned_data['body']

            t = form.save(commit=False)

            t.ip_user = request.META['REMOTE_ADDR']

            words = list(jieba.cut(body, cut_all = True))

            t = form.save()

            tags_list = []

            for word in words:

                if word in pctaglist:

                    tags_list.append(word)

                    t.tags.add(word)

                    #问题主要在这里， pctaglist 是在后台添加的 标签tags, #用jieba分词分析文章内容后得出来的词与这个后台添加的标签取交集。如果有就添加到这个文章的标签里！

                    #这里不知道怎么在这里添加，用t.tags.add(word) 出错:'decimal' codec can't encode characters in position 0-1: invalid decimal Unicode string

                    #要想实现 结巴分词，和现有的 tag 取交集后得出来的词怎么添加到文章的tags里?

            return HttpResponseRedirect(reverse('info:info_detail', kwargs={'pk':t.pk}))

    else:

        form = CreateTopicForm()

        tags_list = []

    return render(request, 'info/post.html', cOntext= {'form':form, 'tags_list':tags_list})