NameError when Passing Variable to a Class Instance in Python

Question

working on a sample battleship game project in python

created a ship class for the various ships here

class Ship:

def __init__(self, ship_name, size, coordinates, direction):
    self.ship_name = ship_name
    self.size = size
    self.coordinates = coordinates
    self.direction = direction

here is my core battleship.py file:

from ship import Ship

SHIP_INFO = [
    ("Aircraft Carrier", 5),
    ("Battleship", 4),
    ("Submarine", 3),
    ("Cruiser", 3),
    ("Patrol Boat", 2)
]

BOARD_SIZE = 10

VERTICAL_SHIP = '|'
HORIZONTAL_SHIP = '-'
EMPTY = 'O'
MISS = '.'
HIT = '*'
SUNK = '#'

board=[]
for row in range(10):
    board.append('O'*10)


def clear_screen():
    print("\033c", end="")


def print_board_heading():
    print("   " + " ".join([chr(c) for c in range(ord('A'), ord('A') + BOARD_SIZE)]))


def print_board(board):
    print_board_heading()
    row_num = 1
    for row in board:
        print(str(row_num).rjust(2) + " " + (" ".join(row)))
        row_num += 1


def coord_prompt():
    while True:
        coords = input("Where do you want the ship + (example: A1)?: ")
        coords_strip = coords.strip()
        coords_lower = coords_strip.lower()
        x = coords_lower[0]
        y = coords_lower[1:]

        if (len(x)+len(y)) in range(2,4):
            if x not in 'abcdefghij' or y not in '1,2,3,4,5,6,7,8,9,10':
                print("Oops!  That was not a valid entry.  Try again...")
                continue

            else:
                return x,y
        else:
            if len(coords_lower) < 2 or len(coords_lower) > 3:
                print("Oops!  That's too not the right amount of characters. Please try again...")
                continue


def pos_prompt():
    while True:
        dir = input("[H]orizontal or [V]ertical?")
        dir_strip = dir.strip()
        dir_lower = dir_strip.lower()

        if dir_lower not in 'hv':
            print("Oops!  That was not a valid entry.  Try again...")
            continue

        else:
            return dir_lower


def make_ships(player):
    ships = []
    for ship, size in SHIP_INFO:
        coord_prompt()
        pos_prompt()
        ships.append(Ship(ship, size, (x, y), dir_lower))
    return ships

player1 = input("What's Player 1's Name? ")
player2 = input("What's Player 2's Name? ")
print("\n")
print_board(board)
print("\n")

# define player one's fleet
make_ships(player1)

i'm getting the following error:

Traceback (most recent call last):
  File "C:/Users/chrisstuart/Desktop/battleship/battleship/battleship.py", line 91, in <module>
    make_ships(player1)
  File "C:/Users/chrisstuart/Desktop/battleship/battleship/battleship.py", line 81, in make_ships
    ships.append(Ship(ship, size, (x, y), dir_lower))
NameError: name 'x' is not defined

I just don't understand why the returned x and y variables from the coord_prompt function are not passing to the ship instance of Ship when running the make_ships function. I assumed it was a problem with the way that I had formatted some of the if statement and the while loop and tried a few variations but still getting same error.

its your coord_prompt() line, you're not getting the return values, try this instead: x, y = coord_prompt() — RichSmith
– RichSmith, Commented Mar 3, 2017 at 14:49

Daniel Roseman · Accepted Answer · 2017-03-03 14:48:12Z

2

Because you haven't captured the return values in the calling function in order to use them in the subsequent call.

The names x and y are local to coord_prompt and are not preserved once that function finishes. The values are returned, but you still need to assign them to something. The same is true of the value returned from pos_prompt.

    x, y = coord_prompt()
    dir_lower = pos_prompt()
    ships.append(Ship(ship, size, (x, y), dir_lower))

answered Mar 3, 2017 at 14:48

Daniel Roseman

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2 Comments

John Rogerson Over a year ago

Thank you! Very helpful. Quick question--if i want to get the name of the ship into the coord_prompt function -- coords = input("Where do you want the ship + (example: A1)?: ") is there an easy way to do that?

Daniel Roseman Over a year ago

Sure, you would need to make the name a parameter to the coord_prompt function.

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