class CourseDetailView(View):
    课程详情页
    def get(self, request, course_id):
        course = Course.objects.get(id=int(course_id))
        #增加课程点击数
        course.click_nums +=1
        course.save()
        tag = course.tag
        if tag:
            relate_courses = Course.objects.filter(tag=tag)[:1]
        else:
            relate_courses = []
        return render(request, "course-detail.html", {
            "course":course,
            "relate_courses":relate_courses
Exception Location:
C:\Users\Edward\PycharmProjects\MxOnline\apps\courses\views.py in get, line 60
Python Executable:
C:\Users\Edward\Envs\mxonline\Scripts\python.exe
Python Version:
2.7.11
Python Path:
['C:\\Users\\Edward\\PycharmProjects\\MxOnline\\extra_apps',
'C:\\Users\\Edward\\PycharmProjects\\MxOnline\\apps',
'C:\\Users\\Edward\\PycharmProjects\\MxOnline',
'C:\\Users\\Edward\\PycharmProjects\\MxOnline\\extra_apps',
'C:\\Users\\Edward\\PycharmProjects\\MxOnline\\apps',
'C:\\Users\\Edward\\PycharmProjects\\MxOnline',
'C:\\WINDOWS\\SYSTEM32\\python27.zip',
'C:\\Users\\Edward\\Envs\\mxonline\\DLLs',
'C:\\Users\\Edward\\Envs\\mxonline\\lib',
'C:\\Users\\Edward\\Envs\\mxonline\\lib\\plat-win',
'C:\\Users\\Edward\\Envs\\mxonline\\lib\\lib-tk',
'C:\\Users\\Edward\\Envs\\mxonline\\Scripts',
'd:\\program files\\python27\\Lib',
'd:\\program files\\python27\\DLLs',
'd:\\program files\\python27\\Lib\\lib-tk',
'C:\\Users\\Edward\\Envs\\mxonline',
'C:\\Users\\Edward\\Envs\\mxonline\\lib\\site-packages']
Server time:
星期四, 19 一月 2017 22:46:59 +0800
因为在前端HTML页面收到返回的relate_courses内容是空，
但是在前端会将relate_courses内容循环迭代输出，即便没有值也需要relate_courses 是一个数组
HTML代码：
{% for relate_course in relate_courses %}
           <a target="_blank" href="">
               <img width="240" height="220" class="scrollLoading" src="{{ MEDIA_URL }}{{ relate_course.image }}"/>
           <a target="_blank" href=""><h2> django实战项目</h2></a>
           <span class="fl">学习时长：<i class="key">0</i></span>
{% endfor %}