import sys
if sys.version_info.major == 3:
from urllib.parse import urlencode, urlparse, urlunparse, parse_qs
else:
from urllib import urlencode
from urlparse import urlparse, urlunparse, parse_qs
url = 'http://example.com/?a=text&q2=text2&q3=text3&q2=text4'
u = urlparse(url)
query = parse_qs(u.query)
query.pop('q2', None)
u = u._replace(query=urlencode(query, True))
print(urlunparse(u))