Solve 'tuple' object has no attribute 'lower‘

A reproduction of the scene

think ss Is string , Not really ！

ss = ('xyz',)
ss.lower()   #  At this point, it will be reported that the error has been corrected 

Why tuples , It's a string ？ The author's information is as follows
ss = object . attribute ,
object . attribute It's just a string , What is it for? ss But it became a tuple ？

you 're right , That's it , There is a comma after the mistake , Just delete the comma

The solution is to let ss Is string , Otherwise, it can't be adjusted lower()