Professor Simpleton - 1 month ago 5
Python Question

# Two-Dimensional Arrays not updating correctly in python 3

So I am trying to create a simple world generation using code that I currently understand. I am doing this by creating a 2-dimensional array using 0's as nothing and 1's as a drawing function. I first create a blank world using input variables and then I plan to update the array using a generation script. However when trying to update world[0][x] it updates every item at that "x" location throughout every single list

Here is my code:

``````import random

worldHeight = 10 #int(input("What is the world height? "))
worldLength = 5 #int(input("What is the world length? "))
terrainHeight = 5 #int(input("What is the terrain height? "))
step = 2 #int(input("What is the step? "))
world = []
worldBlankRow = []

def createBlank():
global worldLength, worldHeight, world, worldBlankRow
for n in range(0,worldHeight):
worldBlankRow.append(0)
for n in range(0,worldLength):
world.append(worldBlankRow)
print(world)

def generate():
global world, worldHeight, worldLength,terrainHeight
counter=0
#randomStep = random.randint(-(step),step)
#while counter <= worldLength:
for x in range(worldHeight-terrainHeight,worldHeight):
world[0][x] = 1
print(world)
#counter=counter+1
#print(counter)
createBlank()
generate()
``````

and here is my output so you can see what is going wrong:

``````[[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]

[[0, 0, 0, 0, 0, 1, 0, 0, 0, 0], [0, 0, 0, 0, 0, 1, 0, 0, 0, 0], [0, 0, 0, 0, 0, 1, 0, 0, 0, 0], [0, 0, 0, 0, 0, 1, 0, 0, 0, 0], [0, 0, 0, 0, 0, 1, 0, 0, 0, 0]]

[[0, 0, 0, 0, 0, 1, 1, 0, 0, 0], [0, 0, 0, 0, 0, 1, 1, 0, 0, 0], [0, 0, 0, 0, 0, 1, 1, 0, 0, 0], [0, 0, 0, 0, 0, 1, 1, 0, 0, 0], [0, 0, 0, 0, 0, 1, 1, 0, 0, 0]]

[[0, 0, 0, 0, 0, 1, 1, 1, 0, 0], [0, 0, 0, 0, 0, 1, 1, 1, 0, 0], [0, 0, 0, 0, 0, 1, 1, 1, 0, 0], [0, 0, 0, 0, 0, 1, 1, 1, 0, 0], [0, 0, 0, 0, 0, 1, 1, 1, 0, 0]]

[[0, 0, 0, 0, 0, 1, 1, 1, 1, 0], [0, 0, 0, 0, 0, 1, 1, 1, 1, 0], [0, 0, 0, 0, 0, 1, 1, 1, 1, 0], [0, 0, 0, 0, 0, 1, 1, 1, 1, 0], [0, 0, 0, 0, 0, 1, 1, 1, 1, 0]]

[[0, 0, 0, 0, 0, 1, 1, 1, 1, 1], [0, 0, 0, 0, 0, 1, 1, 1, 1, 1], [0, 0, 0, 0, 0, 1, 1, 1, 1, 1], [0, 0, 0, 0, 0, 1, 1, 1, 1, 1], [0, 0, 0, 0, 0, 1, 1, 1, 1, 1]]
``````

as you can see every list is updating where i want to generate one, then the next and then the next.

The problem is that you append `worldBlankRow` to `world`. Now this means that the exact same object is appended many times to `world`. Later, when you change one element of `world`, you change them all, because they are all really pointing to the same `worldBlankRow`. You need a separate copy for each. Try:

``````import random
import copy

worldHeight = 10 #int(input("What is the world height? "))
worldLength = 5 #int(input("What is the world length? "))
terrainHeight = 5 #int(input("What is the terrain height? "))
step = 2 #int(input("What is the step? "))
world = []
worldBlankRow = []

def createBlank():
global worldLength, worldHeight, world, worldBlankRow
for n in range(0,worldHeight):
worldBlankRow.append(0)
for n in range(0,worldLength):
world.append(copy.copy(worldBlankRow))
print(world)

def generate():
global world, worldHeight, worldLength,terrainHeight
counter=0
#randomStep = random.randint(-(step),step)
#while counter <= worldLength:
for x in range(worldHeight-terrainHeight,worldHeight):
world[0][x] = 1
print(world)
#counter=counter+1
#print(counter)
createBlank()
generate()
``````