It looks like you may be using the wrong method. Are you attempting to list all users in your organization and some of their attributes? To do that, you could use something like this:
from arcgis.gis import GIS
gis = GIS("https://www.arcgis.com", username="---", password="---")
userlist = gis.users.search()
for user in userlist:
print("{:<48s}".format(user.fullName), "{:<24}".format(user.email))
This will print the user's name and email address, in two evenly spaced columns. You can add more attributes to that output by using the user['key'] or user.key methods that you would use in a dictionary.