for user in users:
if user != None:
# do stuff with "user"
or more Pythonic, using generators:
for user in (x in users if x != None):
# do stuff with "user"
for user in users:
if user != None:
# do stuff with "user"
or more Pythonic, using generators:
for user in (x in users if x != None):
# do stuff with "user"