Combining Tornado and Flask templates
Tornado templates uses syntax similar to Jinja, but the rendering engine is not Jinja. You might be able to get away with it, but then you would have to keep track of which templates are Jinja and which are Tornado.
For the sake of sanity, just keep them separate.
Is possible to combine Tornado and Flask web templates together? 
For example: Use Index.html as "base" template setting up block for extensions:
Then ,extend index with "block" from Flask for Flask Routes
Then, extend index with "block" from Tornado for Tornado Routes..