fail to indent in inner loop

[perltcl at yahoo.com]

hi

I've started learning python. I was typing from a tutorial,
and I fail to indent on an inner loop.
I got an error and all my previous typed lines are gone.
is there a way to prevent this.
i don't mind editing the last line, but to lose all the previous lines
are too much.
(since it has history function like bash.)