[Tutor] try except continue (fwd)

[Danny Yoo]

---------- Forwarded message ----------
Date: Wed, 24 Aug 2005 11:24:44 -0700
From: tpc247 at gmail.com
Reply-To: tpc at csua.berkeley.edu
To: Danny Yoo <dyoo at hkn.eecs.berkeley.edu>
Subject: Re: [Tutor] try except continue

hi Danny, I finally had a chance to review your explanation of
continue you wrote a while back, and I think I understand it.  You say
the program will filter empty lines from standard input.  I expected
the behavior to be such that, upon running the program, and typing:

hello

Danny

and pressing ctrl-d, I would get:

hello
Danny

Instead, I got the former output, which surprised me.  Why doesn't
your program work as I expected ?  I then wondered what your program
would do if I slightly modified it.  *grin*

import sys

for line in sys.stdin:
    print line

This time, running the same former test, I got the following output:

hello



Danny

As you can see, there are three empty lines now, not just one !  Where
did the extra empty lines come from ?

On 7/28/05, Danny Yoo <dyoo at hkn.eecs.berkeley.edu> wrote:
>
>
> Hi Tpc,
>
> I should have written an example of 'continue' usage to make things more
> explicit.  Here is a simple example:
>
> ###
> """Filters empty lines out of standard input."""
> import sys
> for line in sys.stdin:
>     if not line.strip():
>         continue
>     print line
> ######
>
> This is a small program that filters out empty lines from standard input.
> The 'continue' statement causes us to immediately jump back to the
> beginning of the loop and to keep going.
>
>
>
>
> In Python, continue is intrinstically tied with Python's looping
> operations (while/for).
>
>     http://www.python.org/doc/ref/continue.html
>
> It has very little to do with exception handling, except where the
> footnotes mentions certain artificial limitations in using it within an
> exception-handling block.
>
>