[Tutor] try & except

[John Fouhy]

On 09/08/06, Magnus Wirström <asdlinux at yahoo.se> wrote:
> Hi
>
> I'm playing around with try: and except: i have a code like this
>        try:
>            bibl=os.listdir("c:\\klientdata\\")
>        except:
>            wx.MessageBox("Kunde inte läsa käll
> biblioteket.","Säkerhetskopiering",wx.OK|wx.ICON_ERROR)
>
> (yeah ... it's swedish :) )
>
> So far i get how to use it but i would like to be able to execute the
> try block again after it jumped to the exception. How can i make it
> retry to read the directory?

What logic are you looking for?  Is it ---

  "Try to read directory.  If it doesn't work, try again.  If it still
doesn't work, abort."

or ---

   "Try to read directory.  If it doesn't work, keep trying until it does."

In the former case, you could just put another try block in your except block:

       try:
           bibl=os.listdir("c:\\klientdata\\")
       except:
           wx.MessageBox("Kunde inte läsa käll
biblioteket.","Säkerhetskopiering",wx.OK|wx.ICON_ERROR)
           try:
               bibl=os.listdir("c:\\klientdata\\")
           except:
               wx.MessageBox("Kunde inte läsa käll
biblioteket.","Säkerhetskopiering",wx.OK|wx.ICON_ERROR)

In the latter case, you probably want some kind of loop:

success = False
while not success:
       try:
           bibl=os.listdir("c:\\klientdata\\")
           success = True
       except:
           wx.MessageBox("Kunde inte läsa käll
biblioteket.","Säkerhetskopiering",wx.OK|wx.ICON_ERROR)

Of course, it would be nice to give the users another way out of the loop :-)

HTH!

-- 
John.