在模板文件中&＃xff0c;还能嵌套入模板标签&＃xff0c;做一些特殊处理&＃xff0c;例如流程控制&＃xff0c;下面将简单介绍下模板标签&＃xff0c;主要介绍if和for 标签。
参考官方文档 &＃xff1a; https://docs.djangoproject.com/en/1.5/ref/templates/builtins/
一、for 标签
循环遍历数组中的每个元素&＃xff0c;例如&＃xff0c;展示athletes 列表中的元素&＃xff1a;

    {%forathleteinathlete_list%}
  • {{athlete.name}}
    • {%endfor%}
你可以通过for 标签 &＃xff0c;通过{% for  obj  in  list  reversed %} 遍历列表中的所有元素。
例子1&＃xff1a;
[root&＃64;node1 webproject]# vim jobs/views.py
book_list &＃61; [&＃39;python&＃39;, &＃39;django&＃39;, &＃39;perl&＃39;, &＃39;php&＃39;]
[root&＃64;node1 webproject]# vim jobs/templates/index.html
    {% for bname in book_list %}
  • &＃96;bname&＃96;
    • {% endfor %}


    214625162.png

    如果你需要遍历列表中多个列&＃xff0c;可以把每个子列解包成单独的列。例如&＃xff0c;如果是一个内容包含(x,y)两个元素叫做points 的列表&＃xff0c;你可以通过以下方法输出points的列&＃xff1a;

    {%forx,yinpoints%}There is a point at {{x}},{{y}}{%endfor%}

    这种方法同样适用于当你需要遍历字典键与键值的情况。例如&＃xff0c;如果有个data 字典&＃xff0c;可以通过下面的方法同时输出键和键值&＃xff1a;

    {%forkey,valueindata.items%}{{key}}: {{value}}{%endfor%}

    例子2&＃xff1a;
    [root&＃64;node1 webproject]# vim jobs/views.py
    user &＃61; {&＃39;name&＃39;:&＃39;pmghong&＃39;, &＃39;age&＃39;:23, &＃39;sex&＃39;:&＃39;male&＃39;}
    [root&＃64;node1 webproject]# vim jobs/templates/index.html
      {% for key, value in user.items %}
    • &＃96;key&＃96;: &＃96;value&＃96;
      • {% endfor %}


      214701817.png


      for  还能为每一列设置序号&＃xff0c;例如&＃xff1a;
      VariableDescription
      forloop.counter显示序号&＃xff08;从1开始&＃xff09;
      forloop.counter0显示序号&＃xff08;从0开始&＃xff09;
      forloop.revcounter显示序号&＃xff08;倒序&＃xff0c;从1开始&＃xff09;
      forloop.revcounter0显示序号&＃xff08;倒序&＃xff0c;从0开始&＃xff09;
      forloop.first如果元素是第一个元素&＃xff0c;则返回值为True
      forloop.last如果元素师最后一个元素&＃xff0c;则返回值为True
      forloop.parentloop如果是一个嵌套的循环&＃xff0c;那么引用外面的forloop遍历
      例子3&＃xff1a;
      [root&＃64;node1 webproject]# vim jobs/templates/index.html
    • &＃96;forloop&＃96;.&＃96;counter&＃96;. &＃96;key&＃96;: &＃96;value&＃96;


      • 214757786.png


      for ... empty
      for 标签有一个可选的选项{% empty %} 用于处理没有元素或找不到元素的情况&＃xff1a;

        {%forathleteinathlete_list%}
      • {{athlete.name}}
        • {%empty%}
      • Sorry, no athlete in this list!
        • {%endfor%}
        或者

          {%ifathlete_list%}{%forathleteinathlete_list%}
        • {{athlete.name}}
          • {%endfor%}{%else%}
        • Sorry, no athletes in this list.
          • {%endif%}
        第一种写法相对于第二种更加简洁&＃xff0c;简短还有更高效。
        例子4&＃xff1a;
          {% for athlete in athlete_list %}
        • &＃96; athlete&＃96;.&＃96;name &＃96;
          • {% empty %}
                     
        • Sorry, no athlete in this list!
          • {% endfor %}


          214816865.png


          二、if 标签
          if 标签用作判断&＃xff0c;如果值为True&＃xff08;存在&＃xff0c;不为空&＃xff0c;布尔值不是false&＃xff09;则执行后面的代码块

          {%ifathlete_list%}Number of athletes: {{athlete_list|length}}{%elifathlete_in_locker_room_list%}Athletes should be out of the locker room soon!
          {%else%}No athletes.
          {%endif%}

          上面的例子中&＃xff0c;如果athlete 的不为空&＃xff0c;则显示athlete 的数目。
          我们可以看到&＃xff0c;if 标签能够支持一个或多个{% elif %} 子句&＃xff0c;而{% else %} 后面的代码块将在无法匹配到任何条件的情况下执行。这些子句都是可选的。
          注意&＃xff1a;{% elif %} 子句从Django 1.4.x 以后的版本开始支持。
          布尔值操作
          if 标签能使用and&＃xff0c;or还有not 来测试变量的值或否定变量的值

          {%ifathlete_listandcoach_list%}Both athletes and coaches are available.
          {%endif%}{%ifnotathlete_list%}There are no athletes.
          {%endif%}{%ifathlete_listorcoach_list%}There are some athletes or some coaches.
          {%endif%}{%ifnotathlete_listorcoach_list%}There are no athletes or there are some coaches (OK, sowriting English translations of boolean logic soundsstupid; it&＃39;s not our fault).
          {%endif%}{%ifathlete_listandnotcoach_list%}There are some athletes and absolutely no coaches.
          {%endif%}

          同时使用and 和 or 是允许的&＃xff0c;其中and 的优先级更高&＃xff0c;例如

          {%ifathlete_listandcoach_listorcheerleader_list%}

          等同于&＃xff1a;

          if(athlete_listandcoach_list)orcheerleader_list

          实际上&＃xff0c;使用中括号是无效的语法标记。如果你需要他们来表示优先级,你应该使用嵌套标签。
          if 标签还支持&＃61;&＃61;,!&＃61;,<,>,<&＃61;,>&＃61; 和in 的操作&＃xff1a;
          (1) &＃61;&＃61;

          {%ifsomevar&＃61;&＃61;"x"%}This appears if variable somevar equals the string "x"
          {%endif%}

          (2) !&＃61;

          {%ifsomevar!&＃61;"x"%}This appears if variable somevar does not equal the string "x",or if somevar is not found in the context
          {%endif%}

          (3)<,>

          {%ifsomevar<100%}This appears if variable somevar is less than 100.
          {%endif%}

          {%ifsomevar>0%}This appears if variable somevar is greater than 0.
          {%endif%}

          (4)<&＃61;,>&＃61;

          {%ifsomevar<&＃61;100%}This appears if variable somevar is less than 100 or equal to 100.
          {%endif%}

          {%ifsomevar>&＃61;1%}This appears if variable somevar is greater than 1 or equal to 1.
          {%endif%}

          (5) in
          很多python 容器支持这个操作&＃xff0c;用于判断提供的值是否包含在容器中&＃xff0c;例如下面的例子&＃xff1a;

          {%if"bc"in"abcdef"%}This appears since "bc" is a substring of "abcdef"
          {%endif%}{%if"hello"ingreetings%}If greetings is a list or set, one element of which is the string"hello", this will appear.
          {%endif%}{%ifuserinusers%}If users is a QuerySet, this will appear if user is aninstance that belongs to the QuerySet.
          {%endif%}

          (6)not in
          表示不包含在容器中&＃xff0c;这是一个否定的操作。
          比较运算符不能像在Python或数学符号中“链接”&＃xff0c;例如&＃xff1a;

          {%ifa>b>c%} (错误的&＃xff09;

          正确的表达式&＃xff0c;应该这样&＃xff1a;

          {%ifa>bandb>c%}

          你也可以在表达式中使用过滤器&＃xff0c;例如&＃xff1a;

          {%ifmessages|length>&＃61;100%}You have lots of messages today!
          {%endif%}