Printing indices within two dimensional array relative to specific array coordinates?

Question

Let's say I have an array consisting of multiple lists of .'s, that represent something like a world map. world_array = [['.' * 50 for _ in xrange(50)]

Inside of this array, at index (0, 0), a player variable exists -- a letter p.

How can I go about displaying specific parts of this array to the user based on where their current location is inside of the map? For instance, if I want to display the tile that the player is on, plus the 5-10 tiles around him / her, how could I go about doing that?

P . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .
. . . . . . . . . .

Also, how do I go about print the array in a fashion that removes the brackets and apostrophes associated with lists, like shown above?

Thanks for any answers.

Are you saying the player (the letter p) only starts at (0,0) and can move to other locations? Are you asking only for printing the cells or also some context around the grid to show where the window is in the complete grid? Which version of Python are you using? — Rory Daulton
– Rory Daulton, Commented Aug 6, 2016 at 0:39

Louis Durand · Accepted Answer · 2016-08-16 16:44:04Z

1

First, be careful if you want to modify your map, you should not use strings for the rows because they're immutable. You won't be able to modify your map - unles you rewrite entirely each line.

So I suggest you use this: (A 2D array of chars)

world_map = [['.']*n_cols for _ in xrange(n_rows)]

To print the array as it is:

for row in world_map:
    print ''.join(row)

Now the exploration. If you want to hide the map with dots, then it's not the dots you should store in the 2D array, it is the content of the map.

So let's say I create this map (and these variables):

n_rows = 3
n_cols = 5
world_array = [
['0', '0', '1', '1', '1'],
['0', '2', '0', '1', '0'],
['1', '1', '0', '0', '0']
]
exp_radius = 1 #the player can see 1 square from him
x,y = 1,0 #position of the player

To display the whole map with a visible circle around the player - in (x,y) - and dots elsewhere, then it's like this:

for r in xrange(n_rows):
    row=''
    for c in xrange(n_cols):
        if c=x and r=y:
            row += 'P'
        elif abs(c-x)<=exp_radius and abs(r-y)<=exp_radius:
            row += world_array[r][c]
        else:
            row += '.'
    print row

This would give you:

0P1..
020..
.....

Note that if you prefer a diamond shape rather than a square:

0P1..
.2...
.....

So for the sake of clarity:

..0..
.000.
00P00
.000.
..0..

You should replace the condition:

elif abs(c-x)<=exp_radius and abs(r-y)<=exp_radius:

by:

elif abs(c-x)+abs(r-y)<=exp_radius:

You've got all the clues now, have fun! ;)

EDIT :

If you want to display only the dots for a given width and height around the player, then just modify the range of the for loops like this:

width = 5 # half of the width of the displayed map
height = 3 # half of the height of the displayed map

for r in xrange(max(0,y-height), min(n_rows, y+height)):
    row=''
    for c in xrange(max(0,x-width), min(n_cols, x+width)):
        if c=x and r=y:
            row += 'P'
        elif abs(c-x)<=exp_radius and abs(r-y)<=exp_radius:
            row += world_array[r][c]
        else:
            row += '.'
    print row

So the lines and columns printed will go from the position (x-width, y-height) for top left corner to the position (x+width, y+height) for the bottom right corner and crop if it goes beyond the map. The displayed area is therefore 2*width * 2*height if not cropped.

edited Aug 16, 2016 at 16:44

answered Aug 6, 2016 at 1:05

Louis Durand

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2 Comments

Mochamethod Over a year ago

How would I go about displaying only a small area of the map? This seems to work fine; however, with larger maps, there are a lot of periods everywhere. Could I limit it so that the player is only exposed to an area of 20 or so tiles, instead of printing the whole map?

Louis Durand Over a year ago

Sorry, I was in vacation! :3 I edited my post to add a proposition to do that.

VortixDev · Accepted Answer · 2016-08-06 00:45:12Z

0

Break down your problem. Take a 2D array array[x][y]. If you're wanting to display the tiles up to 5 positions around the player then you must iterate over and print all of those tiles. So, starting from 5 before the player's position and ending 5 afterwards. Logically, it would go as follows (x is first index of player's position, y is second index):

for i = (x - 5) to (x + 5):
    for j = (y - 5) to (y + 5):
        print value of array[i][j]
    end
end

Now, this isn't complete. The reason for that is because, as you may or may not have noticed, this has potential to go out of bounds. This means that if x - 5 < 0 you'll want to start at 0 instead. If x + 5 > array's first dimension's size, you'll want to use the size. There are functions for this - max and min. This means your logic will end up like this:

for i = max(0, (x - 5)) to min(1st dimension's size, (x + 5)):
    for j = max(0, (y - 5)) to min(2nd dimension's size, (y + 5)):
        print value of array[i][j]
    end
end

answered Aug 6, 2016 at 0:45

VortixDev

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1 Comment

VortixDev Over a year ago

Not a language (other than English), it's logical steps rather than code. I won't do everything for OP, just breaking down the process so he understands

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