I just want to know how can i check it is number or not in import sys situation. and want to know Why i didn't get output "Hello" with code A.isalpha()

I just want to know how can i check it is number or not in import sys situation. and want to know Why i didn't get output "Hello" with code A.isalpha()

The method A.isalpha() returns a boolean value True or False not a string "True", you compare booleans like this
if A.isalpha() is True: 
    print("hello")
But as a if expects a boolean statement, the return value from isalpha is already good
if A.isalpha():
    print("hello")
