在python中声明矩阵数组

Question

I'm new in the magic python world.

1)I need to have an array (arrMtx) where each element of this vector is a matrix. How I can declare the array arrMtx?

2)I suppose for filling the arrMtx I should do something like that:

mtx = [[0.0 for x in range(NUM_COLUMN)] for x in range(NUM_ROW)] 
arrMtx[i] = mtx

Do you have any suggestions?

Answer 1

If you want a list of 2d arrays (matrices):

num_matrices = 3 ## Let's say
ncol = 3
nrow = 3
arrMtx = [[[0 for j in range(ncol)] for i in range(nrow)] for k in range(num_matrices)]

Output:

>>>[[[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]]]

Answer 2

Try this simply, where n is no. of elemnts in arrMtx

>>>[[[0.0 for x in range(NUM_COLUMN)] for x in range(NUM_ROW)]]*n #no. of elements

That means

>>>mtx = [[0.0 for x in range(NUM_COLUMN)] for x in range(NUM_ROW)]
>>>arrMtx = [mtx] * n

Answer 3

NUM_COLUMN = 4
NUM_ROW = 2
NUM_MATRIX = 3
mtx = [[0.0 for x in range(NUM_COLUMN)] for x in range(NUM_ROW)] 
arrMtx = [mtx for x in range(NUM_MATRIX)]
print arrMtx

Output:

[[[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, 0.0, 0.0, 0.0], [0.0, 0.0, 0.0, 0.0]]]

Answer 4

In Python, Lists are use like vector in c++ .

In a list, you can append as you like:

L = [0,1,2,3....]

After append list will be:

L.append('str')
L = [0,1,2,3,'str'....]

So, you can anything append you can want.

So make a matrix , you need list of list like:

L = [[....], [.....]....]

mtx = [[0.0 for x in range(NUM_COLUMN)] for x in range(NUM_ROW)]

Here mtx is also a matrix . you can append it into another list:

arrMtx = [] 
arrMtx.append(mtx)

Question 1 answer:

You can declare the array arrMtx like:

arrMtx = []

It's create a list. Then you append a list, it will be an array.