I want to calculate complex eigenvectors (Psi functions for shrodinger equation) for 20k*20k matrices, but always gets smth like this:

[  2.99009782e-09  -1.12381299e-08  -2.82346868e-08 ...,   6.20967928e-34
  -4.80675528e-34  -3.84848719e-35]
[  4.07337553e-08  -1.45976681e-07  -3.47961439e-07 ...,   7.43558322e-34
  -5.74815572e-34  -4.61317607e-35]
[  5.51921102e-07  -1.88491289e-06  -4.26000711e-06 ...,   9.29535407e-34
  -7.15304083e-34  -5.78846547e-35]

As I understand it just replaces part of data with dots, it’s strange. May be there is a problem with saving data in file? My code is attached:

import numpy as np
import math
import scipy.linalg as la
from numpy.linalg import eigvalsh
def potential(i):
    return -1/(10*(math.cos((i/2-5)*math.pi/10)-1)*(math.cos((i/2-5)*math.pi/10)-1)+1)
def element(i,j):
    if i==j:
        return 0.1524+potential(i)
    if abs(i-j)==1:
        return -0.1524/2
    return 0
I = 1j
a=[]
for i in range(0,2000):
    b=[]
    for j in range(0,2000):
        b.append(element(i,j))
    a.append(b)
arr = np.array(a)
print('matrix created')
eigvals, eigvecs = la.eig(arr)
print('eigenvalues and eigenvectors calculated')
eigvals = eigvals.real
f = open('Energies.txt', 'w')
for element in eigvals:
    f.write(str(element)+'\n')
print("eigenvalues stored")
f = open('Psi_functions.txt', 'w')
for element in eigvecs:
    f.write(str(element)+'\n')

>Solution :

Use np.savetxt

np.savetxt('Energies.txt', eigvals)

np.savetxt('Psi_functions.txt', eigvecs)

Use np.loadtxt to load them:

eigvals2 = np.loadtxt('Energies.txt')

eigvecs2 = np.loadtxt('Psi_functions.txt')

>>> (eigvals == eigvals2).all()
True

>>> (eigvecs == eigvecs2).all()
True