import ldap
url = 'ldap://10.15.120.250'
user = 'myusername@post.ad'
password = 'pass'
conn = ldap.initialize(url)
conn.protocol_version = 3
conn.set_option(ldap.OPT_REFERRALS, 0)
conn.simple_bind_s(user, password)

conn.search_ext('cn=base,dc=example,dc=com', ldap.SCOPE_SUBTREE, '(sn=Johnson)')