# Battleship Exercise

#1

Hi. For the Battleship Exercise, see my code below:

It is working fine, however, I just want my code to accept that if a user/player enters a string or a null value, it wouldn't error out to:

Traceback (most recent call last):
File "python", line 32, in
ValueError: invalid literal for int() with base 10: 's'

I want my code to be able to catch this. Probably be under "Oops, that's not even in the ocean." part.
I've tried adding an elif wherein when guess_row or guess_col != int, but it does not work.

Any inputs would be appreciated and thank you in advance!

``````Replace this line with your code.

from random import randint

board = []

for x in range(5):
board.append(["O"] * 5)

def print_board(board):
for row in board:
print " ".join(row)

print "Let's play Battleship!"
print_board(board)

def random_row(board):
return randint(0, len(board) - 1)

def random_col(board):
return randint(0, len(board) - 1)

ship_row = random_row(board)
ship_col = random_col(board)

print ship_row
print ship_col

# Everything from here on should go in your for loop!
# Be sure to indent four spaces!

for turn in range(4):

guess_row = int(raw_input("Guess Row:"))
guess_col = int(raw_input("Guess Col:"))

if guess_row == ship_row and guess_col == ship_col:
print "Congratulations! You sunk my battleship!"
break
else:
if (guess_row < len(board) or guess_row > len(board)) or (guess_col < len(board) or guess_col > len(board)):
print "Oops, that's not even in the ocean."
print_board(board)
if turn == 3:
print "Game Over"
elif(board[guess_row][guess_col] == "X"):
print "You guessed that one already."
print_board(board)
if turn == 3:
print "Game Over"
else:
print "You missed my battleship!"
board[guess_row][guess_col] = "X"
print_board(board)
if turn == 3:
print "Game Over"
# Print (turn + 1) here!
print "Turn", turn + 1``````

#2

The best solution would be let the user try again, with a while loop. But in order to do so, we need to learn something we haven't: try and except. this allows you to catch errors:

``````while True:
try:
guess_row = int(raw_input("Guess Row:"))
except ValueError:
print("Sorry, I didn't understand that.")
else:
break``````

#3

So in the _except ValueError: all non integers will fall under that? Also, is it possible to catch this through an if else logic, instead?

Thanks! I'll definitely try this one but I just haven't reached that lesson yet (if it will be covered in this course).

#4

Thanks! Tried it already and it worked!

#5

try except isn't teached in this course. You can use isistance, in combination with if/else and a while loop