Comprobación de si una web carga de forma rapida y sencilla.

estaviva.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

try:
    import urllib2  # Python 2
except ImportError:
    import urllib.request as urllib2  # Python 3


def isup(url):
    try:
        if not url.startswith(("http://", "https://")):
            url = "http://" + url

        rq = urllib2.Request(
            url,
            headers={
                'User-Agent': 'Mozilla/5.0 (X11; Linux x86_64; rv:40.0) Gecko/20100101 Firefox/40.0'
            }
        )
        rq.get_method = lambda: 'HEAD'

        urllib2.urlopen(rq)
        return "Carga sin problemas."
    except urllib2.HTTPError as e:
        return "Carga pero da el siguiente error: %s" % (e)
    except urllib2.URLError:
        return "No carga."


urls = (
    'http://httpbin.org/get',
    'http://httpbin.org/status/404',
    'http://httpbin.org/status/500',
    'http://httpbin.ogr/',
    'httpbin.org/get',
    'httpbin.org',
    'https://httpbin.org/get'
)

for u in urls:
    print("Probando %s... %s" % (u, isup(u)))