如何为用户提供安全模板以便用python进行修改？

I am building a multi-user web application. Each user can have their own site under my application. I am considering how to allow user to modify template without security problem? I have evaluated some python template engine. For example, genshi, it is a pretty wonderful template engine, but however it might be dangerous to allow user to modify genshi template. It have a syntax like this:I am building a multi-user web application. Eac