Store coordinates in 2d grid

Question

I`m writing a function for small pygame program. The ideas is that I have a 500 pixels square screen and I want to place 5 objects per row with the size of width and height in random order and I need a function to generate and store coordinates.

from random import randint

def gen_coords(width=50, height=50, side_of_scr=500):
    """Generates random coordinates for objects in rows
    that are positioned on 5x5 grid."""

    coords = []
    for row in range(5):
        # creating row container
        coords.append([])
        for pos in range(5):
            # range of values in randint reflects that i want the objects
            # to be placed with offset of the sides of the screen
            x = randint(0.5 * width, side_of_scr - 0.5 * width)

            # the distance between the rows is equal to the height of an object
            y = 0.5 * height + row * 2 * height
            coords[row].append((x, y))
    return coords

So this

for coord in gen_coords():
    print(coord)

returns

[(177, 25.0), (367, 25.0), (214, 25.0), (284, 25.0), (125, 25.0)]
[(425, 125.0), (446, 125.0), (126, 125.0), (409, 125.0), (187, 125.0)]
[(210, 225.0), (188, 225.0), (215, 225.0), (132, 225.0), (431, 225.0)]
[(303, 325.0), (471, 325.0), (252, 325.0), (26, 325.0), (111, 325.0)]
[(468, 425.0), (127, 425.0), (452, 425.0), (30, 425.0), (345, 425.0)]

I've done this using list of lists and it's working so far, but im looking for the better way to do it. Thanks for help.

Answer 1

I am not entirely sure what you are unhappy about, so I am going to assume you find it too cumbersome, so here is a "one line" way to do it:

import random
gen_coords = (lambda rows=range(5), cols=range(5): lambda width=50, height=50, side_of_scr=500: [[
    (random.randint(width/2, side_of_scr - width/2), height/2 + row * 2 * height)
    for col in cols] for row in rows])()

That is still ugly, so let us make an elegant solution, with better performance:

import random
def gen_coords(width=50, height=50, side_of_scr=500, rows=5, cols=5):
    lower = width/2
    upper = side_of_scr - width/2
    height_step = 4 * height
    gen_x = lambda : random.randint(lower, upper)
    def gen_row(row):
        y = (row + 0.25) * height_step
        return [(gen_x,y) for col in range(cols))]
    return [gen_row(row) for row in range(rows)]