dict_testing.py

def groups_per_user(group_dictionary):
    user_groups = {}
    # Go through group_dictionary
    for group, users in group_dictionary.items():
        for user in users:
            if user not in user_groups:
                user_groups[user] = []
            user_groups[user].append(group)
#user_groups[user].append(group)          
# Now add the group to the the list of
# groups for this user, creating the entry
# in the dictionary if necessary
    return(user_groups)

print(groups_per_user({"local": ["admin", "userA"],
		"public":  ["admin", "userB"],
		"administrator": ["admin"] }))