Thanks Mark & Rhodri. Neither works. I'm using Notepad2 as editor. Don't use the tab. Each space counted with spacebar & recounted. Rewrote the block from scratch as new script and eliminated the print line in the loop. Now no error message, but it will go on forever despite repeatedly entering 0. Have to get out with ctrl-c .
while True : num = int(input()) if num == 0 : break print('done') Frusting: I'm missing something fundamental. Dave WB3DWE -- http://mail.python.org/mailman/listinfo/python-list