Username Validity Checker

import re

pts=0
a={
    1:"May only consist of alphanumeric characters",
    2:"This username is valid",
   }
b=0

username=input("")

alnum=re.search(r"\W" or r"\s",username )

if not alnum:
    pts+=1
    b=2
if alnum:
     b=1

print("Username:",username )
if pts==    1:
    print(a[b])
else:
    print(a[b])