Problem with the input

[buran]

not clear what you are having problem with

>>> user = 'marios'
>>> user + '@'
'marios@'

or better - using f-strings (string-formatting)

>>> email = f'{user}@python-forum.io'
>>> email
'[email protected]'

please post minimal reproducible example. If you get any traceback - post it in full, in error tags