Ndtyjky

After I sort this numpy array and remove all duplicate (y) values and the corresponding (x) value for the duplicate (y) value, I use a for loop to draw rectangles at the remaining coordinates. yet I get the error : ValueError: too many values to unpack (expected 2), but its the same shape as the original just the duplicates have been removed.

from graphics import *

import numpy as np



def main():

    win = GraphWin("A Window", 500, 500)



# starting array

startArray = np.array([[2, 1, 2, 3, 4, 7],

              [5, 4, 8, 3, 7, 8]])



# the following reshapes the from all x's in one row and y's in second row

# to x,y rows pairing the x with corresponding y value.

# then it searches for duplicate (y) values and removes both the duplicate (y) and

# its corresponding (x) value by removing the row.

# then the unique [x,y]'s array is reshaped back to a [[x,....],[y,....]] array to be used to draw rectangles.

d = startArray.reshape((-1), order='F')



# reshape to [x,y] matching the proper x&y's together

e = d.reshape((-1, 2), order='C')



# searching for duplicate (y) values and removing that row so the corresponding (x) is removed too.

f = e[np.unique(e[:, 1], return_index=True)[1]]



# converting unique array back to original shape

almostdone = f.reshape((-1), order='C')



# final reshape to return to original starting shape but is only unique values

done = almostdone.reshape((2, -1), order='F')



# print all the shapes and elements

print("this is d reshape of original/start array:", d)

print("this is e reshape of d:n", e)

print("this is f unique of e:n", f)

print("this is almost done:n", almostdone)

print("this is done:n", done)

print("this is original array:n",startArray)



# loop to draw a rectangle with each x,y value being pulled from the x and y rows

# says too many values to unpack?

for x,y in np.nditer(done,flags = ['external_loop'], order = 'F'):

    print("this is x,y:", x,y)

    print("this is y:", y)

    rect = Rectangle(Point(x,y),Point(x+4,y+4))

    rect.draw(win)



win.getMouse()

win.close()



main()

here is the output:

line 42, in main

for x,y in np.nditer(done,flags = ['external_loop'], order = 'F'):

ValueError: too many values to unpack (expected 2)

this is d reshape of original/start array: [2 5 1 4 2 8 3 3 4 7 7 8]

this is e reshape of d:

 [[2 5]

 [1 4]

 [2 8]

 [3 3]

 [4 7]

 [7 8]]

this is f unique of e:

 [[3 3]

 [1 4]

 [2 5]

 [4 7]

 [2 8]]

this is almost done:

 [3 3 1 4 2 5 4 7 2 8]

this is done:

 [[3 1 2 4 2]

 [3 4 5 7 8]]

this is original array:

 [[2 1 2 3 4 7]

 [5 4 8 3 7 8]]

why would the for loop work for the original array but not this sorted one?
or what loop could I use to just use (f) since it is sorted but shape(-1,2)?

I also tried a different loop:

for x,y in done[np.nditer(done,flags = ['external_loop'], order = 'F')]:

Which seems to fix the too many values error but I get:

IndexError: index 3 is out of bounds for axis 0 with size 2

and

FutureWarning: Using a non-tuple sequence for multidimensional indexing is 

deprecated; use `arr[tuple(seq)]` instead of `arr[seq]`. In the future this 

will be interpreted as an array index, `arr[np.array(seq)]`, which will 

result either in an error or a different result.

  for x,y in done[np.nditer(done,flags = ['external_loop'], order = 'F')]:

which I've looked up on stackexchange to fix but keep getting the error regardless of how I do the syntax.

any help would be great thanks!

I don't have the graphics package (it might be a windows specific thing?), but I do know that you're making this waaaaay too complicated. Here is a much simpler version that produces the same done array:

from graphics import *

import numpy as np



# starting array

startArray = np.array([[2, 1, 2, 3, 4, 7],

                       [5, 4, 8, 3, 7, 8]])



# searching for duplicate (y) values and removing that row so the corresponding (x) is removed too.

done = startArray.T[np.unique(startArray[1,:], return_index=True)[1]]



for x,y in done:

    print("this is x,y:", x, y)

    print("this is y:", y)

    rect = Rectangle(Point(x,y),Point(x+4,y+4))

    rect.draw(win)

To note, in the above version done.shape==(5, 2) instead of (2, 5), but you can always change that back after the for loop with done = done.T.

Here's some notes on your original code for future reference:

• The order flag in reshape is completely superfluous to what your code is trying to do, and just makes it more confusing/potentially more buggy. You can do all of the reshapes you wanted to do without it.




• The use case for nditer is to iterate over the individual elements of one (or more) array one at a time. It cannot in general be used to iterate over the rows or columns of a 2D array. If you try to use it this way, you're likely to get buggy results that are highly dependent on the layout of the array in memory (as you saw).




• To iterate over rows or columns of a 2D array, just use simple iteration. If you just iterate over an array (eg for row in arr:), you get each row, one at a time. If you want the columns instead you can transpose the array first (like I did in the code above with .T).

Note about .T

.T takes the transpose of an array. For example, if you start with

arr = np.array([[0, 1, 2, 3],

                [4, 5, 6, 7]])

then the transpose is:

arr.T==np.array([[0, 4],

                 [1, 5],

                 [2, 6],

                 [3, 7]])