Is there an idiomatic file extension for Jinja templates?

Question

I need to programatically distinguish between Jinja template files, other template files (such as ERB), and template-less plain text files.

According to Jinja documentation:

A Jinja template doesn’t need to have a specific extension: .html, .xml, or any other extension is just fine.

But what should I use when an explicit extension is required? .py is misleading, and any search including the words "jinja" and "extension" are badly searchwashed by discussion around Jinja Extensions.

I could easily dictate a project-wide convention (.jnj or .ja come to mind) but this is for open source so I don't want to buck the trend if there's already established practice somewhere.

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EDIT 1: Again, I understand that the Jinja project — purposefully — does not define a default file extension. I'm asking if there are any unofficial conventions that have emerged for circumstances where one is desired for some project-specific reason.

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EDIT 2: Clarification: This is not for HTML content.

Answer 1

Ansible uses the .j2 extension.

I couldn't find a definitive documentation about that precise point but we see occurences of the .j2 extension in many places of their documentation :

If you look for .j2 in the following pages you'll see many occurences :

http://docs.ansible.com/ansible/template_module.html http://docs.ansible.com/ansible/playbooks_intro.html

This is the convention that I use for other projects as well, except django templates.