Does the placement of this line of code matter?

Question

This is Kenneth's code:

import os
import random

# draw grid
# pick random location for player
# pick random location for exit door
# pick random location for the monster
# draw player in the grid
# take input for movement
# move player, unless invalid move (past edges of grid)
# check for win/loss
# clear screen and redraw grid

CELLS = [(0, 0), (1, 0), (2, 0), (3, 0), (4, 0),
         (0, 1), (1, 1), (2, 1), (3, 1), (4, 1),
         (0, 2), (1, 2), (2, 2), (3, 2), (4, 2),
         (0, 3), (1, 3), (2, 3), (3, 3), (4, 3),
         (0, 4), (1, 4), (2, 4), (3, 4), (4, 4)]


def clear_screen():
    os.system('cls' if os.name == 'nt' else 'clear')


def get_locations():
    return random.sample(CELLS, 3)


def move_player(player, move):
    x, y = player
    if move == "LEFT":
        x -= 1
    if move == "RIGHT":
        x += 1
    if move == "UP":
        y -= 1
    if move == "DOWN":
        y += 1
    return x, y


def get_moves(player):
    moves = ["LEFT", "RIGHT", "UP", "DOWN"]
    x, y = player
    if x == 0:
        moves.remove("LEFT")
    if x == 4:
        moves.remove("RIGHT")
    if y == 0:
        moves.remove("UP")
    if y == 4:
        moves.remove("DOWN")
    return moves


monster, door, player = get_locations()

while True:
    valid_moves = get_moves(player)
    clear_screen()
    print("Welcome to the dungeon!")
    print("You're currently in room {}".format(player))
    print("You can move {}".format(", ".join(valid_moves)))
    print("Enter QUIT to quit")

    move = input("> ")
    move = move.upper()

    if move == 'QUIT':
        break
    if move in valid_moves:
        player = move_player(player, move)
    else:
        print("\n ** Walls are hard! Don't run into them! **\n")
        continue

    # Good move? Change the player position
    # Bad move? Don't change anything!
    # On the door? They win!
    # On the monster? They lose!
    # Otherwise, loop back around

I have an issue with the placement of

monster, door, player = get_locations()

Does it matter if that line is just before the while loop or can it be placed anywhere? Does it affect the order of initialisation of these variables or something??

Answer 1 · 2018-12-19T12:27:51Z

December 19, 2018 12:27pm

Python statements are executed sequentially and so order is important

If I do something like this

hello()

def hello():
      print("hello")

This code will give a NameError, because the code that declares the hello() function has not yet been executed.

So in your case

monster, door, player = get_locations()

has to be called after the get_locations() function.

He could have placed it just after the

def get_locations():
    return random.sample(CELLS, 3)

but I think it was good presentation to declare all your functions 1st

Secondly, the monster, door and player variables have to be declared before the while loop, because they are referenced within the while loop. If the code was placed after the while loop, an error will be generated

Take note that for the same reason;

move_player(player, move)
get_moves(player)

functions also needed to be declared before the while loop.

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