python 3.3 urllib.request

[Hans Mulder]

On 7/12/12 13:52:52, Steeve C wrote:
> hello,
> 
> I have a python3 script with urllib.request which have a strange
> behavior, here is the script :
> 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> #!/usr/bin/env python3
> # -*- coding: utf-8 -*-
> 
> import urllib.request
> import sys, time
> 
> 
> url = 'http://google.com'
> 
> def make_some_stuff(page, url):
>     sys.stderr.write(time.strftime("%d/%m/%Y %H:%M:%S -> page from \"")
> + url + "\"\n")
>     sys.stderr.write(str(page) + "\"\n")
>     return True
> 
> def get_page(url):
>     while 1:
>         try:
>             page = urllib.request.urlopen(url)
>             yield page
> 
>         except urllib.error.URLError as e:
>             sys.stderr.write(time.strftime("%d/%m/%Y %H:%M:%S ->
> impossible to access to \"") + url + "\"\n")
>             time.sleep(5)
>             continue
> 
> def main():
>     print('in main')
>     for page in get_page(url):
>         make_some_stuff(page, url)
>         time.sleep(5)
> 
> if __name__ == '__main__':
>     main()
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 
> if the computer is connected on internet (with an ethernet connection
> for example) and I run this script, it works like a charme :
> - urllib.request.urlopen return the page
> - make_some_stuff write in stderr
> - when the ethernet cable is unplug the except block handle the error
> while the cable is unplug, and when the cable is pluged
> back urllib.request.urlopen return the page and make_some_stuff write in
> stderr
> 
> this is the normal behavior (for me, imho).
> 
> but if the computer is not connected on internet (ethernet cable
> unpluged) and I run this script, the except block handle the error
> (normal), but when I plug the cable, the script continue looping
> and urllib.request.urlopen never return the page (so, it always
> go to the except block)
> 
> What can I do to handle that ?

On my laptop, your script works as you'd hope: if I plug in the
network cable, then the next urllib request sometimes fails, but
the request after that succeeds.
This is using Python 3.3 on MacOS X 10.5.
What version are you running?

What happens if you start the script with the network cable
plugged in, then unplug it when the first request has succeeded,
and then plug it in again when the next request has failed?

-- HansM