missing items from python lists

Question

I have two functions that generates two matrices, the first function generate some square matrix, while the second one generate a 1D matrix depending on the first matrix. Both functions depend on parameter N, the second function matrix result should have a matrix with (N*2)**2 .My problem is when i use a value of the parameter N grater than 4 their is always 10 missing elements from the second function result.(The OP functions have been deleted to create a minimal question. Check the edit for details. An example function is below demonstrating the issue

def test(N):
        m = []
        for i in range(0,(N*2)):
            for j in range(-1,(N*7),4):
                m.append((i,j))


        return len(m)

example for N = 4

test(4)

Output:
64

example for N = 5

test(5)

Output:
90

The result in example 2 is 90 while it should be 100, can anyone help please

Answer 1

You can easily check how many iterations either range will cause:

>>> n = 5
>>> len(range(0, n*2))
10
>>> len(range(-1, n*7, 4))
9

10*9 is indeed a total of 90 iterations and 90 elements added to the array.

I'm assuming you expect more elements from the inner loop, so probably you are confused about how range treats boundaries. The quick solution is to try variations like n*7+1 until you get the correct behavior.