See Python-Markdown-Editor  
It is based on : 
- Python-Markdown
 
- Pygments (code block syntax highlighting)
 
- CodeMirror (javascript code editor)
 
- Bottle
 
Install with pip : 
$ pip install markdown-editor 
It features when-you-type preview, code highlight, fenced code blocks, github style
it can be used by commandline : 
$ markdown_edit 
$ markdown_edit README.md
$ markdown_edit -f readme.html README.md

I created this to build a tool for sending code reviews, it is easily extensible, by importing it as a module you can add custom actions.