#!/usr/bin/python
import re
cadena = "Link(base_url='file:/home/alejandro/Escritorio/1biinox.php.html', url='http://vale.com/scripts/runner.php?IM=45b2a2ec96953.', text='* Ejemplo* aquamails', tag='a', attrs=[('href', 'http://vale.com/scripts/runner.php?IM=45b2a2ec96953.'), ('target', '_inbox')])";
print cadena, "\n\n";
t = cadena[cadena.find("http://"):]
print t,"\n";
t = t[:t.find(" ")]
print t

http://www.amk.ca/python/howto/regex/
http://docs.python.org/library/re.html#re-syntax
http://stackoverflow.com/questions/520031/whats-the-cleanest-way-to-extract-urls-from-a-string-using-python