To get input from the person running your script, you can use the function input(). And to get the length of your variable you can call len().

hello.py

my_name = input("Please tell me your name: ")

name_length = len(my_name)

print(f"Hello {my_name}! Your name is {name_length} characters long")

Please tell me your name: Jean
Hello Jean! Your name is 4 characters long