flask多选框怎么实现

<form class="form-horizontal" method="post">

    <div class="form-group">

      <label for="username" class="col-sm-2 control-label">Username</label>

      <div class="col-sm-10">

        <input type="text" class="form-control" id="username" name="username" placeholder="Username" autofocus="" >

      </div>

    </div>

....

...

  <div class="row">

        <div class="col-sm-2 col-sm-offset-2">

            <input name="sex" value="M" type="radio"  checked="checked"> 男

        </div>

 <div class="col-sm-2 ">

            <input name="sex" value="F" type="radio"> 女

        </div>

    </div>

</form>

if request.method == "POST":  

    username = request.values.get("username")

    sex = request.values.get("sex")

<div class="row">

    <div class="col-sm-2 ">

        <label>

            <input name="s_option" value="basketball" type="checkbox"> 篮球

        </label>

    </div>

    <div class="col-sm-2 ">

        <label>

        <input name="s_option" value="football" type="checkbox"> 足球

        </label>

    </div>

    <div class="col-sm-2 ">

        <label>

            <input name="s_option" value="badminton"  type="checkbox"> 羽毛球

        </label>

    </div>

</div>