Launching pdb from within a script

[Graham Nicholls]

I asked this before, but got no response, but I KNOW YOU KNOW ;-)
A year or so ago, I was given a really useful answer to a question posed
here, which showed me how to start the debugger from withing a script. 
Yes, of course I've lost the mail (and I have trawled through all my old
mail), and yes, I know I'm stupid!

I'm surprised this isn't a FAQ, BTW, as it seems such a  useful facility.

So come on guys, cough it up!
Thanks
Graham Nicholls
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#include <wit>