[web2py] How to accomplish post excerpt

[ola . dipo30]

{{ for post in posts:}}
   <h2>
     <a href="{{=URL(r=request,f='view_post',args=post.id)}}">
       {{=post.title}}
     </a>
   </h2>
{{=WIKI(post.body|truncate:30)}}
{{pass}}

Thanks in avance. something similar to Django |truncate:x

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