Youtube extension for Python-Markdown
Python-Markdown docs
Flask-Markdown docs
Replacing:
[youtube]https://www.youtube.com/watch?v=udlMSe5-zP8[youtube]
with youtube embed code
<div class="youtube">
<iframe src="https://www.youtube.com/embed/moPtwq_cVH8" frameborder="0" allowfullscreen class="video"></iframe>
</div>