Rep:EnergyAndMagnetisation.py:

import numpy as np

class IsingLattice:
   E = 0.0
   E2 = 0.0
   M = 0.0
   M2 = 0.0
   n_cycles = 0

   def __init__(self, n_rows, n_cols):
       self.n_rows = n_rows
       self.n_cols = n_cols
       self.lattice = np.random.choice([-1,1], size=(n_rows, n_cols))
 
   def energy(self):
       "Return the total energy of the current lattice configuration."
       energy = 0.0
       
       sum_sisj  = []
       
       for i in range(self.n_rows): 
           for j in range(self.n_cols):
           
               if i < self.n_rows -1:
                   sum_sisj.append(self.lattice[i,j] * self.lattice[i+1,j])
               else:
                   sum_sisj.append(self.lattice[i,j] * self.lattice[0,j])

               if i > 0:
                   sum_sisj.append(self.lattice[i,j] * self.lattice[i-1,j])
               else:
                   sum_sisj.append(self.lattice[i,j] * self.lattice[self.n_rows -1,j])
               
               if j < self.n_cols -1:
                   sum_sisj.append(self.lattice[i,j] * self.lattice[i,j+1])
               else:
                   sum_sisj.append(self.lattice[i,j] * self.lattice[i,0])  
               
               if j > 0:
                   sum_sisj.append(self.lattice[i,j] * self.lattice[i,j-1])
               else:          
                   sum_sisj.append(self.lattice[i,j] * self.lattice[i,self.n_cols -1])       
       sum_sum_sisj = sum(sum_sisj)       
       E = -0.5 * 1.0 * sum_sum_sisj
       return E

   def magnetisation(self):
       "Return the total magnetisation of the current lattice configuration."        
       magnetisation_list = []
       
       for i in range(self.n_rows): 
           for j in range(self.n_cols):
               magnetisation_list.append(self.lattice[i,j])
       magnetisation = sum (magnetisation_list)           
       return magnetisation