Never Ending Validation Check in Python

Question

Working on a battleship game in python. My function to check the user's 'guess' input in resulting in an endless validation loop. I want a guess in the format of 'a10' on a 10x10 grid. The validation function i have built to help validate is as follows:

 def validate_guess(self,guess):
 while True:
 if (len(guess)) in range(2, 4):
 if guess[0] not in 'abcdefghij' or guess[1:] not in '1,2,3,4,5,6,7,8,9,10':
 print("Sorry the Grid is a 10x10 square you must enter a valid position. Try again...")
 continue
 else:
 return guess
 else:
 if len(guess) < 2 or len(guess) > 3:
 print("Oops! That's too not the right amount of characters. Please try again...")
 continue

If the user guesses an incorrect value--it does spot it--but the error is returning a never ending loop with the printed error statement.

This is the portion of my game where the validation function is being used:

while True:
 print("\n")
 # get guess from player one in coordinate form (example: a10)
 guess = input("{}'s turn to guess: ".format(player1.player))
 # strip characters from the guess input
 guess = guess.strip()
 # validate the guess
 guess = self.validate_guess(guess)
 # append the guess to a list for player 1
 player1.guesses.append(guess)
 # break down the coordinates into x and y variables
 x, y = ship1.split_guess(guess)
 # increment guesses
 guesses += 1
 # loop to assess whether, hit, miss or a won game
 if any(guess in ship for ship in grid2.play_two_board):
 print("HIT")
 grid2.print_guess_board(x, y, "h")
 for ship in grid2.play_two_board:
 try:
 ship.remove(guess)
 print(len(Board.play_two_board))
 self.check_if_sunk(ship)
 win = self.play_one_win_check(player1.player)
 if win == 1:
 print ("GAVE OVER!")
 break
 except ValueError:
 pass
 else:
 print("Miss!")
 grid2.print_guess_board(x, y, "m")

Not sure if it might be because i have two While statements? Just really stuck here would appreciate any guidance. Thanks.

*****************************8 edit --changed function to include the guess without actually passing it that value from the input statement but still getting same problem.

 def validate_guess(self):
 guess = input("Please enter a location:")
 while True:
 if len(guess) in range(2, 4):
 if guess[0] not in 'abcdefghij' or guess[1:] not in '1,2,3,4,5,6,7,8,9,10':
 print("Sorry the Grid is a 10x10 square you must enter a valid position. Try again...")
 continue
 else:
 return guess
 else:
 if len(guess) < 2 or len(guess) > 3:
 print("Oops! That's too not the right amount of characters. Please try again...")
 continue

and just calling it like this:

while True:
 print("\n")
 # get guess from player one in coordinate form (example: a10)
 # guess = input("{}'s turn to guess: ".format(player1.player))
 # strip characters from the guess input
 # guess = guess.strip()
 # validate the guess
 guess = self.validate_guess()

• roganjosh: while True: in def validate_guess(self,guess): doesn't appear to make sense. guess is an argument that you pass to the function. It retains the same value whilst that function runs because nothing in the function modifies or redefines it. If it doesn't satisfy the conditions to reach a return statement in its first pass through your checks, it never will. Your while loop then only serves to do the same, failing, validation checks over and over forever.
• Prune: Possible duplicate of Prompt the user to input something else if the first input is invalid
• John Rogerson: thanks -- i think i understand what you are referring to--i edited code (As shown above) to include input statement in the function--but still getting the same error.
• John Rogerson: never mind i got it--thank you

Answer 1

Within validate_guess, when the user enters a bad value, you have to get new input before you check again. See here.

Either return an error code (True/False ?) from your function, or have the function loop until the input is valid. Just add a command for new input at the bottom of the function's while loop.

• John Rogerson: hmm--ok so i added the input statement within the function (without passing the guess variable) and still getting the same problem --see edited code above
• John Rogerson: ahh. never mind--i didn't put input statement within the while statement--woops. thanks for you help.