This link was exactly what I was searching for .
Let me summarize the answers for others' benefit (for python and notepad++)
1) Ctrl+K on multiple lines (i.e. selected region) allows you to block comment.
Also note that pressing the combination multiple times allows you to add multiple "#"s (sometimes I use that while testing to differentiate from other comments)
2) Ctrl+Shift+K (on the commented region) allows you to perform block uncomment
3) Ctrl+Shift+K on an uncommented selected region does not comment it
4) Ctrl+Q allows you to block comment/uncomment in a toggled mode (meaning, you cannot add multiple '#'s like in 1) )
Hope this helps another wandering soul.
Question - how would you develop a hack of keyboard combinations to comment/uncomment if there were no shortcuts? Just curious. I've no clue hence asking.