I would like to be able to create a variable that was an N x N matrix and that each of the positions in the matrix would be a list of two elements.
and be able to assign them in a similar way to this, within a for loop:
matriz[1][2]=[345.545, 415.213]
How do I define the variable matrix? I've tried something like:
matriz = np.array(N,N), dtype=list)
but it does not work well.
If you want to access a list or a array with the operator [][] , you just have to put a list within another list, in Python 2 and 3 you can do it in the same way:
# Suponiendo que N sean 10 items:
N = 10
# Creamos la lista de NxN listas.
matriz = list([ list([]) for i in range(0, N) ] for k in range(0, N))
matriz[1][2] = [ 345.545, 415.213 ]
print(matriz) # imprime la lista.
You should print:
[
[[], [], [], [], [], [], [], [], [], []],
[[], [], [345.545, 415.213], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []],
[[], [], [], [], [], [], [], [], [], []]
]
If I have not confused what you want is a three-dimensional array, that is, an NxN matrix where each element is an array / list of one dimension with two elements. Since you work with NumPy you should use a np.array and not a list for each element of the matrix. You can start your matrix with all the elements to 0 using numpy.zeros :
>>> import numpy as np
>>> N = 3
>>> matriz = np.zeros((N,N,2))
>>> matriz[1][2]=[345.545, 415.213]
>>> matriz
array([[[ 0. , 0. ],
[ 0. , 0. ],
[ 0. , 0. ]],
[[ 0. , 0. ],
[ 0. , 0. ],
[ 345.545, 415.213]],
[[ 0. , 0. ],
[ 0. , 0. ],
[ 0. , 0. ]]])