Python is determined whether a valid identifier

String member operator: in

Determining whether a character string in another string

'a' in 'abcd' #Ture

'e' in 'abcd' #False

. 1  Import String
 2  
. 3 all_chars = string.ascii_letters string.digits + + ' _ ' 
. 4  
. 5 NUM = INPUT ( " Please enter the string ' )
 . 6  for I in NUM:
 . 7      IF I in all_chars:
 . 8          Print ( ' valid ' )