python - how to use while loop to print 'not allowed' message when there is space between characters

Question

i wanted while loop to work when there is spaces between character but it didn't.

a= input("...")
x = [" "]

while a in :
  print("not allowed")

question from:https://stackoverflow.com/questions/66057261/how-to-use-while-loop-to-print-not-allowed-message-when-there-is-space-between

Answer 1

a= input("...")
x = [" "]

while " " in a:
  print("not allowed")