如果声明不在Jinja工作

Question

我正在使用jija2。我不确定天气我错过了什么，但提到的if语句（{%if actors%}...{%endif%}）似乎不起作用。

actors是电影名称列表。

{%if actors%}
  {%block movies%}
     <div class='card-activity col-md-4' id="material-card-info">
        <table class="table table-striped table-hover ">
           <thead>
        <tr>
        <th><h5 style="color:#E91E63; font-weight:lighter; font-height:;">Actors</h5></th>
        </tr>
        </thead>
        <tbody>
        {%for actor in actors%}
            <tr><td>{{actor}}</td></tr>
        {%endfor%}
        </tbody>
      </table> 
    </div>
  {%endblock%}
{%endif%}

这是视图功能：

@app.route('/movie/<b64>')
def profile_movie(b64):
    profile = database_search_withid(b64) #returns a tuple eg: ('Avatar', 2012, ['Sam Worthington', 'Zoe Saldana'])
    if not profile:
        abort(404)
    cast= json.loads(profile[2]) #list of actors obtained above is json
    actor, actress = filter_feature(cast) #returns actor and actress in separate list
    print show
    return render_template('movie_profile.html', song_entries=profile, actors=actor, actresses=actress)

即使列表为空，div内的{%if actors%}也会显示。我错过了什么？