On 12/7/2012 12:27 PM, Hans Mulder wrote:
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 ?
Don't do 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?
I believe he said that that worked. But unplugging cables is not a good
idea ;-)
I remember when it was recommended that all cables be plugged in and the
the connected devices turned on when the computer was turned on and when
devices might not be recognized unless plugged in and on when the
computer was booted or rebooted. In other words, ports were scanned once
as part of the boot process and adding a device required a reboot. It
certainly was not that long ago when I had to reboot after the Internet
Service went down and the cable modem had to reset.
Ethernet and usb ports and modern OSes are more forgiving. But it does
not surprise me if on some systems something has to be presence at
process startup to evet be visible to the process.
I believe this is all beyond Python's control. So the only thing to do
might be to change hardware and/or OS or have the program restart itself
if it gets repeated errors.
--
Terry Jan Reedy
--
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