Andrey K

def frange(end, start=0.0, step=0.1):
     i = start
     while i < end:
         yield i
         i += step

class BaseClass:
    @classmethod
    def get_prefix(cls):
        raise NotImplemented('Переопределите этот метод в дочернем классе')

    @classmethod
    def get_string_with_prefix(cls, string=''):
        return cls.get_prefix() + string

class ChildClass(BaseClass):
    @classmethod
    def get_prefix(cls):
        return 'child_class_prefix_'

l = [a,b,c]
l.sort()
print('Max:', l[2])
print('Min:', l[0])
print('Other:', l[1])

import urllib2
from lxml import html

data = urllib2.urlopen(url).read()
h = html.fromstring(data)
h.cssselect('.mv_actions a')[0].attrib['href']