使用Selenium和Python定位，在文本框中输入值

<div class="MY_HEADING_A">
    <div class="TitleA">My title</div>
    <div class="Foobar"></div>
        <div class="PageFrame" area="W">                
             <span class="PageText">PAGE <input id="a1" type="txt" NUM="" />  of <span id="MAX"></span> </span>
</div>
<div class="MY_HEADING_A">
    <div class="Titl