How do I check make sure I don’t have duplicates. (Python)

Question

Im trying to figure out where/how do I compare my two variables in lower() to make sure any variations of a username are rejected. My code is:

current_users = [‘Denis’, ‘Liz’, ‘Jim]
new_users=[‘denis’, ‘Tom’, ‘Sara’, ‘JIM]

for new_users in new_users:

if new_users in current_users:
print( “username {new_users} is unavailable”)

else:
print(“ {new_users} is available “)

Answer 1

This is the correct code:
current_users = ['Denis', 'Liz', 'Jim']
new_users = ['denis', 'Tom', 'Sara', 'JIM']

#converting usernames to lowercase.
current_users = [x.lower() for x in current_users]
new_users = [x.lower() for x in new_users]

for new_users in new_users:
if new_users in current_users:
print( f"{new_users} is unavailable")
else:
print(f"{new_users} is available")
#there might be shorter and better way of doing this.