How do I get the position in a 2D Numpy array when iterating?

user_4778238 0
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I have a 2D Numpy array representing a level map in a tile-based game I'm making in Python3.7. My array is 50 rows x 50 columns, and each value is an integer number representing a sprite type (various wall parts, floors, etc). When I iterate through the array and find a wall sprite (for example), I want to know the row and column number of that value so I can reference it directly.

It seems such a simple thing, but I can't seem to find the right Numpy function that will iterate through the 2D array and return the position[row, col]of each one it finds. I can then calculate it's relative position on the screen using the array position, and then test collision with .colliderect().

EDIT: For more clarity, I'm adding the fact that I need to compare each integer value in the array to aList of wall parts (also integers), and if it's in the list, return the array position.

TL;DR How do I iterate through a Numpy 2darray and return the[row, col] for each match instead of the value?

numpy-ndarray python-3.x numpy arrays python
2 Answers

Just use np.argwhere.

Example:

>>> import numpy as np
>>> a = np.zeros((50, 50))
>>> a[3, 4] = 1
>>> a[4, 5] = 1
>>> for i, j in np.argwhere(a == 1): print(i, j)
... 
(3, 4)
(4, 5)

(The above example was run using python 2, hence the tuples in the output shown, but it is otherwise exactly the same in python 3.)

user_135960370

I'm thinking that you could use nested for-loops and a data structure like below:

let's say map is a 2-D numpy array and that 1 represents a wall type and 2 represents a floor type.

code:

locationsToSprites = dict()#Data structure that stores the locations of the sprite type. 
for row in range(0, len(map)): #looping through all rows
    for col in range(0, len(map[row])):#looping through all columns of a row
        if(map[row][col] == 1):
            locationsToSprites[(row, col)] = 'the wall type'
        elif(map[row][col] == 2):
            locationsToSprites[(row, col)] = 'the floor type'

Now, because a dictionary was used to store the locations of the sprites we can just print the keys of the dictionary to get all the locations.

user_40084850
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