if z:
print 'a'
print 'b'Sure, when you paste code somewhere that expects prose (Facebook status updates, for example), it will consolidate consecutive whitespace and thereby remove the indentation, but you shouldn't be pasting code into a place like that anyway, because no matter what you do it'll be unreadable, and most people aren't going to be interested enough to put it into their editor to autoformat.
But the OP's point is that you can't know how many lines make up the indented block, since there is no explicit block-end-marker left if the indent is gone.
Except if you have, for example, an if statement. if x: y() is valid.