Python array and function

Question

I have a list 'map' and I want to replace all elements by the respectives output values of a function "counterPosition" that acts on each position of the initial array, something like that:

map[0][0] = counterPosition(0,0)
map[0][1] = counterPosition(0,1)
...

Doing one by one like that I can get the answer, but when I try something like that:

 for x in range (len(map)):
    for y in range (len(map)):
        map[x][y] = counterPosition(x,y)

It doesn't work... Am I doing something wrong?

EDIT:

def counterPosition(x, y):
    bombs = 0
    for i in range(x-1, x+2):
        for j in range(y-1, y+2):
            if i<0 or j<0: continue
            elif map[i][j] == True:
                bombs += 1
    return bombs

map = [[True, False, False, False, False, True],
         [False, False, False, False, False, True],
         [True, True, False, True, False, True],
         [True, False, False, False, False, False],
         [False, False, True, False, False, False],
         [False, False, False, False, False, False]]

The error is:

IndexError: list index out of range

Do you have a numpy array, or a standard python list (nested) instead? — Martijn Pieters
– Martijn Pieters, Commented Feb 27, 2013 at 22:27
map = [[True, False, False, False, False, True], [False, False, False, False, False, True], [True, True, False, True, False, True], [True, False, False, False, False, False], [False, False, True, False, False, False], [False, False, False, False, False, False]] — user2083363
– user2083363, Commented Feb 27, 2013 at 22:31
"It' doesn't work..." is not a very elaborate problem description. Do you get an error? Which python version are you using? You realize, that you are using a) a list (not an array) b) you override the builtin map function. — Don Question
– Don Question, Commented Feb 27, 2013 at 22:35
As a side note: It's a bad idea to name a variable map, as that's a built-in function (and one that might even be directly useful to your problem…). — abarnert
– abarnert, Commented Feb 27, 2013 at 22:36

YXD · Accepted Answer · 2013-02-28 10:24:42Z

3

You were nearly there

for x in range (len(map)):
    for y in range(len(map[x])):
        map[x][y] = counterPosition(x,y)

Update: The original code you gave will only run as long as your map is square, but this is the case for the data you provided. Looking at your sample data and updated code, the actual error is coming from your counterPosition function. Actually there are two problems.

1. In your counterPosition function you accessing elements that are out of range. This is printed as part of the error message right above IndexError:... - it's a good idea to read these messages carefully and include it in your post. If you pass in x=5,y-5 then the function will try and access map[6][6]. The "correct" code should be something like

def counterPosition(x, y):
    bombs = 0
    for i in range(x-1, x+2):
        for j in range(y-1, y+2):
            # check bounds:
            if 0 <= i < len(map) and 0 <= j < len(map[i]):
                if map[i][j] == True:
                    bombs += 1
    return bombs

2. The second problem is that counterPosition expects map to contain boolean elements, however you are returning an integer from counterPosition and assigning that to map[x][y]. So the next time round map will contain integer values. Without seeing the rest of your project, I think what you want are two separate multi-dimensional arrays.

edited Feb 28, 2013 at 10:24

answered Feb 27, 2013 at 22:28

YXD

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1 Comment

Gerrat Over a year ago

...and Mr. E's implementation works fine for me with your data, and an arbitrary counterPosition function, so it's something else you're doing wrong

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