Dear Adel,

At first thank you for your reply and your help. In fact I tried A[i,j] in the past but it does not work in my code. Please look at the following:

import numpy as np
import matplotlib.pyplot as plt
from functools import partial

import kwant
from kwant.physics import dispersion

def make_lead_with_crossing_bands():
    lat = kwant.lattice.square(1)
    sym = kwant.TranslationalSymmetry((-2, 0))
    H = kwant.Builder(sym)
    H[lat(0, 0)] = 0
    H[lat(0, 1)] = 0
    H[lat(1, 0)] = 0
    H[lat(1, 0), lat(0, 0)] = 1
    H[lat(2, 1), lat(0, 1)] = 1
    H[lat(2, 0), lat(1, 0)] = 0.5
    return H

lead = make_lead_with_crossing_bands().finalized()
bands = dispersion.Bands(lead)

momenta = np.linspace(-np.pi,np.pi, 500)
energies = [bands(k) for k in momenta]
ax1=bands(-np.pi)

print ('ax1=',ax1)

print ('ax1=',ax1[0,1])

here ax1 is a matrix with dimension 1*3. I want to use element ax1(1,2), But according to the ax1[0,1], it gives me an error with massage "too many indices for array". That is very kind of you if you help me.

Best,

Nafise

On Sat, Dec 7, 2019 at 3:27 PM Abbout Adel <abbout.adel@gmail.com> wrote:

Dear Nafise,

Your question is a python related question. You can find the answer in any python documentation or forum.

So please, make an effort and search around you or by a quick check on internet before posting a question in the kwant forum. 

In fact, posting non kwant related questions in this forum, makes it a general forum rather than a specialized one. 

So for your question if A is a matrix, the elements are A[i,j].   

Example A=array([[1,2],[3,4]])   gives A[0,0]=1.

I hope this helps,

Ade

On Sat, Dec 7, 2019 at 8:26 AM Nafise Nouri <nafise.nour@gmail.com> wrote:

Dear all,

Is there any one to know how we can use one element of matrix? For example we have matrix A as follows:

A=[2 4;6,0]

We have A matrix with dimension 2*2. If  we want to use one element of matrix such as A(2,1), (that is number 6 in the matrix), How we can write in kwant? Any help appreciate.

Best,

Nafise

--

Abbout Adel