Convert a matrix to a list

Question

I'm working with numpy using a matrix that is 1x3. My question is:
Exists a way to convert that matrix into a tuple that contains the elements of the matrix in order? For example, if the matrix is

A=matrix([[1,2,3]])

get

B=(1,2,3)

But my problem is that the word 'matrix' exists and when you get something in the matrix, it still has the word 'matrix' at the start. — iam_agf, Dec 25 '13 at 04:29
you can extract undelying array with `matrix([[1,2,3]]).A`, or flattened 1d underlying array with `matrix([[1,2,3]]).A1`, and work with them — alko, Dec 25 '13 at 07:29

Justin O Barber · Accepted Answer · 2013-12-25T04:41:11.993

3

Yes, you can do something as simple as this:

>>> A = matrix([[1,2,3]])
>>> B = A.tolist()
>>> B
[[1, 2, 3]]
>>> B = A.tolist()[0]
>>> B
[1, 2, 3]

EDIT:

As Christian points out, I see that you have changed your desired output to a tuple. As Christian suggests, all you need to do is this:

>>> B = tuple(A.tolist()[0])
>>> B
(1, 2, 3)

A will still function as a matrix, but B is now a tuple and so will not function as a matrix.

edited Dec 25 '13 at 04:41

answered Dec 25 '13 at 04:24

Justin O Barber

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Thanks! If the matrix is of 3x1 still works? – iam_agf Dec 25 '13 at 04:31
Remember that to convert a list into a tuple just do: `B = tuple(list_here)` – Christian Tapia Dec 25 '13 at 04:36

falsetru · Answer 2 · 2013-12-25T07:33:33.140

1

If you want get a list from 3x1, 1x3, use flatten:

>>> from numpy import matrix
>>> matrix([[1,2,3]]).flatten().tolist()[0]
[1, 2, 3]
>>> matrix([[1],[2],[3]]).flatten().tolist()[0]
[1, 2, 3]

Alternative using A1 attribute:

>>> matrix([[1],[2],[3]]).A1.tolist()
[1, 2, 3]
>>> matrix([[1,2,3]]).A1.tolist()
[1, 2, 3]

edited Dec 25 '13 at 07:33

answered Dec 25 '13 at 04:42

falsetru

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In first case adding `flatten()` doesn't do anything, you can just do `matrix([[1,2,3]]).tolist()[0]`. – Akavall Dec 25 '13 at 04:47
@Akavall, added `flatten()` to make sure it work for both case. – falsetru Dec 25 '13 at 04:49
I used, and results useful. Thanks! – iam_agf Dec 25 '13 at 04:56
1

I don't like this `[0]`, one option would be `np.matrix([[1],[2],[3]]).A1.tolist()` – alko Dec 25 '13 at 07:30
@alko, Thank you for comment. I updated the answer with your code. – falsetru Dec 25 '13 at 07:33

Akavall · Answer 3 · 2013-12-25T04:57:38.623

0

How about this?

>>> import numpy as np
>>> m = np.matrix([[1,2,3]])
>>> m
matrix([[1, 2, 3]])
>>> B = tuple(m.A[0])
>>> B
(1, 2, 3)

Edit: Inspired by @falsetru's use of flatten, this is a more general solution:

>>> tuple(m.A.flatten())
(1, 2, 3)

I think using flatten on an array makes more sense because it converts 2D array into 1D, while this cannot be done for matrices.

edited Dec 25 '13 at 04:57

answered Dec 25 '13 at 04:41

Akavall

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Convert a matrix to a list

3 Answers3