Plotting an array in Python

Question

I'm trying to plot a generated array in Python. The array is generated from maze.txt as you can see below. The result is an array composed of only 0's and 1's where each 0 and 1 represents one grid square on the map. The 0's are boundaries, this can be black or any color for that matter, and the 1's are the path that has been navigated.

Searching around I thought that matplotlib could accomplish what I'm trying to do but I'm not quite sure how to implement it. I'm very inexperienced with Python. Thank you for any suggestions/help.

file = open("maze.txt", 'r')
arr = []
for line in file.readlines():
    #print();
    arr1 = []
    for c in line:
        if(c.isspace() and (c!="\n")):
            arr1.append(1)
            #print("1",end="")
        elif(c!="\n"):
            arr1.append(0)
            #print("0",end="")

    arr.append(arr1)
#print()
#print(arr)
for row in arr:
    print(row)

Below is an example of 'maze.txt'

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |                             |
+ + +-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| | |       |   |   |         | |
+ + + +-+ +-+ + + + + +-+-+-+ + +
| | | | |     | | | | |   |   | |
+ + + + +-+-+-+ + + + +-+ + +-+ +
| | | |         | | | |     |   |
+ + + + +-+-+-+ + + + +-+ +-+ + +
| | | | |   | | | |   |   | | | |
+ + + + + + + +-+ +-+-+ +-+ + + +
| | | |   | |     |       |   | |
+ + + +-+-+ + +-+-+-+ +-+-+ + + +
| | | |     | |   |     | | | | |
+ + + + + +-+ + + + +-+-+ + + + +
| | | | | |   |         |   | | |
+ + + + +-+ +-+-+-+-+-+ + + + + +
| | | | |     |       | | | | | |
+ + + + + +-+-+-+-+ + + + +-+-+ +
| | | | |   |       | | |     | |
+ + + + + + + +-+ +-+ + +-+-+ + +
| | | |   | |       | |     | | |
+ + + +-+-+ +-+ +-+ + +-+-+ + + +
| |   |     |       | |   | | | |
+ +-+ + +-+-+ +-+ +-+ + + + + + +
|   | |             |   |   | | |
+ + + +-+-+-+-+-+-+-+-+-+-+-+ + +
| | |                         | |
+ + +-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |                             |
.-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Which is converted to:

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0]
[0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]
[0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0]
[0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0]
[0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0]
[0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0]
[0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0]
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

@Craig Error

Do you have an example of `maze.txt` and what the output should be? — Eric Duminil, Apr 08 '17 at 20:51

Craig · Accepted Answer · 2017-04-09T12:59:33.727

3

You can use the pcolormesh() command in matplotlib to plot an array of values.

import matplotlib.pyplot as plt

plt.pcolormesh(arr)
plt.axes().set_aspect('equal') #set the x and y axes to the same scale
plt.xticks([]) # remove the tick marks by setting to an empty list
plt.yticks([]) # remove the tick marks by setting to an empty list
plt.axes().invert_yaxis() #invert the y-axis so the first row of data is at the top
plt.show()

The additional lines help improve the appearance of the maze by setting the axes x and y scales equal (to make it square) and by removing the x an y tick marks.

EDIT

Added the line plt.axes().invert_yaxis() to invert the plot so that it appears in the same orientation as the array (with row 0 at the top). By convention, matplotlib plots arr[0,0] in the bottom left corner. Inverting the y-axis move this to the top left corner.

This code produces the following image:

edited Apr 09 '17 at 12:59

answered Apr 08 '17 at 21:29

Craig

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Thank you for your response. What you show looks exactly like what I was aiming for. When I try it in my code it throws an error. "ValueError: need more than 1 value to unpack". – super_not_super_user Apr 09 '17 at 03:09
I also just realized the image you show is actually vertically mirrored from what it should be. – super_not_super_user Apr 09 '17 at 05:23
@super_not_super_user - Easy fix :) I've updated the code to orient the maze correctly. Please be sure to accept this answer (grey check mark) if it solves your problem. – Craig Apr 09 '17 at 13:01
Still can't get it to work from within Ubuntu. I installed Anaconda in Windows and it seems to work just fine though. Thanks a lot for your help! – super_not_super_user Apr 09 '17 at 20:11

Plotting an array in Python

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