The Markdown Smart_Strong Extension adds smarter handling of double underscores within words. This does for double underscores what smart_emphasis does for single underscores.
The Smart_Strong Extension is included in the standard Markdown library.
>>> import markdown
>>> markdown.markdown('Text with double__underscore__words.', \
extensions=['smart_strong'])
u'<p>Text with double__underscore__words.</p>'
>>> markdown.markdown('__Strong__ still works.', \
extensions=['smart_strong'])
u'<p><strong>Strong</strong> still works.</p>'
>>> markdown.markdown('__this__works__too__.', \
extensions=['smart_strong'])
u'<p><strong>this__works__too</strong>.</p>'
This extension is also included with the Extra Extension. You may call that extension to get this behavior with all the other features of 'Extra'.
>>> markdown.markdown(text, extensions=['extra'])