def ishex(c):
 return (('0' <= c <= '9') or ('a' <= c <= 'f') or ('A' <= c <= 'F'))

def ishex ( c ) : return ( ( '0' <= c <= '9' ) or ( 'a' <= c <= 'f' ) or ( 'A' <= c <= 'F' ) )
return true if the byte ordinal c is a hexadecimal digit in ascii .