Traceback (most recent call last):
  File "script.py", line 7, in <module>
    proxy = urllib2.ProxyHandler(line)
  File "/usr/lib/python2.7/urllib2.py", line 713, in __init__
    assert hasattr(proxies, 'has_key'), "proxies must be a mapping"
AssertionError: proxies must be a mapping

import urllib2
u=open('urls.txt')
p=open('proxies.txt')
for line in p:
    proxy = urllib2.ProxyHandler(line)
    opener = urllib2.build_opener(proxy)
    urllib2.install_opener(opener)
    for url in u:
        urllib.urlopen(url).read()

u.close()
p.close()

'www.google.com'
'www.facebook.com'
'www.reddit.com'

{'https': 'https://94.142.27.4:3128'}
{'http': 'http://118.97.95.174:8080'}
{'http':'http://66.62.236.15:8080'}

p=open('proxies.txt')
for line in p:
    proxy = urllib2.ProxyHandler(line)

p=open('proxies.txt')
for line in p:
    d = ast.literal_eval(line)
    proxy = urllib2.ProxyHandler(d)

{"https": "https://94.142.27.4:3128"}
{"http": "http://118.97.95.174:8080"}
{"http": "http://66.62.236.15:8080"}

import json
import urllib2

with open('proxies.txt') as proxies:
    for line in proxies:
        proxy = json.loads(line)
        proxy_handler = urllib2.ProxyHandler(proxy)
        opener = urllib2.build_opener(proxy_handler)
        urllib2.install_opener(opener)
with open('urls.txt') as urls:
    for line in urls:
        url = line.rstrip()
        data = urllib.urlopen(url).read()
        # do something with data

with open('urls.txt') as f:
    urls = [line.rstrip() for line in f]
with open('proxies.txt') as proxies:
    for line in proxies:
        proxy = json.loads(line)
        proxy_handler = urllib2.ProxyHandler(proxy)
        opener = urllib2.build_opener(proxy_handler)
        urllib2.install_opener(opener)
        for url in urls:
            data = urllib.urlopen(url).read()
            # do something with data