create file of valid web proxies usuing python

I need a simple script that automatically gets a list of possible valid web proxies. Program must be in written in python. requirements 1.) program must pull proxy list (instead of push) 2.) program pulls from at least 3 different webpages/sources 3.) each source page should return at least 15 proxies (I can provide the test script to determine if a proxy is valid.) 4.) cant use vpngeeks, 2freeproxy, or [login to view URL]