Python - Traversing and modifying 2d array not working

Question

I have a 2d Array named Matrix. The array is populated with a bunch of o's and c's. I am trying to traverse the array element by element. If an element meets a certain set of rules, I would like to change the element to an N.

Below is my code for doing so. When I run my code, some elements are replaced with an N, but not all of the elements that should be.

I would really appreciate your help as to why this is happening, thanks!

2D Array:

https://nofile.io/f/74GXSntofsG/obstaclemapinput.txt

Outputted 2D Array:

https://nofile.io/f/ZhzK38x4Sqp/obstaclemap.txt

Code:

matrix_icrement_width = int(width/int(boxsize))
matrix_icrement_height = int(height/int(boxsize))
Matrix =  [[0 for x in range(matrix_icrement_width)] for y in range(matrix_icrement_height)] 

#The 2d array is populated however that code is long and irrelevant so I did not include it in my question 

def traverse_matrix():
for i in range (0,matrix_icrement_width):
    for j in range (0,matrix_icrement_height):
        if Matrix[i][j]== "o":
            #if u r on a wall, dont do anything
            break

        if Matrix[i][j-1] == "o":
            #if u were on a wall, but not anymore
            Matrix[i][j] = "N"

        if Matrix[i+1][j] == "c":
            #if the space below u is a path
            Matrix[i][j] = "N"

        if Matrix[i][j+1] == "o":
            #if the space infront of u is a wall
            Matrix[i][j] = "N"



def printMatrix():
    f = open('obstaclemap.txt', 'w')
    f.write('\n'.join([''.join(['{:4}'.format(item) for item in row]) 
      for row in Matrix]))
    f.close()

traverse_matrix()
printMatrix()

could your break be the problem? i mean ok you don't want to do anything when the index is at the edge but by using break u go out of your loop without iterating though all the elements. At least thats what it looks like to me at a mere glance. You should make use of additional conditonal for the controlflow and stay away from break in this case if you ask me. — The Fool
– The Fool, Commented Aug 13, 2018 at 18:14

Krishna Choudhary · Accepted Answer · 2018-08-13 18:28:05Z

I think the issue is due to careless use of break instead of continue. Try substituting it and let me know the results.

matrix_icrement_width = int(width/int(boxsize))
matrix_icrement_height = int(height/int(boxsize))
Matrix =  [[0 for x in range(matrix_icrement_width)] for y in range(matrix_icrement_height)] 

#The 2d array is populated however that code is long and irrelevant so I did not include it in my question 

def traverse_matrix():
for i in range (0,matrix_icrement_width):
    for j in range (0,matrix_icrement_height):
        if Matrix[i][j]== "o":
            #if u r on a wall, dont do anything
            continue         #Modify this

        if Matrix[i][j-1] == "o":
            #if u were on a wall, but not anymore
            Matrix[i][j] = "N"

        if Matrix[i+1][j] == "c":
            #if the space below u is a path
            Matrix[i][j] = "N"

        if Matrix[i][j+1] == "o":
            #if the space infront of u is a wall
            Matrix[i][j] = "N"



def printMatrix():
    f = open('obstaclemap.txt', 'w')
    f.write('\n'.join([''.join(['{:4}'.format(item) for item in row]) 
      for row in Matrix]))
    f.close()

traverse_matrix()
printMatrix()

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