from urlparse import urlparse
import sys

try:
    o = urlparse(sys.argv[1])
    if not o[0]:
        1/0
    print 'eto url, mamoy klyanus!'
except:
    print 'net, eto ne url, urlom ne vishel...'

[8:30] u@notebook:~> cat /usr/ports/www/py-urlwatch/pkg-descr
With urlwatch you can watch changes in webpages and get notified (via e-mail,
in your terminal or through various third party services) of any changes.

The change notification will include the URL that has changed and a unified
diff of what has changed.

WWW: https://github.com/thp/urlwatch

<?php exit((isset($argv[1]) ? ('Это' . (filter_var($argv[1], FILTER_VALIDATE_URL) ? ' ' : ' НЕ ') . 'урл') : 'Введите урл!') . PHP_EOL);