diff --git a/fcc_ge.py b/fcc_ge.py
index 984106c..2500275 100644
--- a/fcc_ge.py
+++ b/fcc_ge.py
@@ -20,7 +20,7 @@ def main():
         eigs_k.append(eigs)
 
     eigs_k = np.array(eigs_k).T
-    print eigs_k[:,-1]
+    print(eigs_k[:,-1])
     draw_band(kpts_len, eigs_k)
 
 
diff --git a/hamiltonian.py b/hamiltonian.py
index 63f0cdc..651ac97 100644
--- a/hamiltonian.py
+++ b/hamiltonian.py
@@ -51,7 +51,7 @@ def calc_g(self, kpt):
                     phase = np.exp(2.*np.pi*1j * np.dot(kpt_cart, dist_vec))
                     g_mat[image_ind, ind_1, ind_2] = phase 
         # non-translated image_ind is self.system.structure.max_image/2
-        g_mat[self.system.structure.max_image/2, :, :] += np.eye(self.n_orbitals, dtype=complex)
+        g_mat[self.system.structure.max_image//2, :, :] += np.eye(self.n_orbitals, dtype=complex)
         return g_mat
 
     def calc_ham_wo_k(self):
@@ -109,8 +109,10 @@ def get_ind(atom_1_i, orbit_1_i, element_1, orbit_1):
 
             onsite_i = self.system.get_onsite_term(atom_i)
 
-            self.H_wo_g[self.system.structure.max_image/2, 
-                        H_ind: H_ind+len_orbitals, H_ind: H_ind+len_orbitals] = onsite_i
+            #print(self.system.structure.max_image//2, H_ind, (H_ind+len_orbitals), H_ind,(H_ind+len_orbitals) )
+            #exit()
+            self.H_wo_g[self.system.structure.max_image//2, 
+                        (H_ind):(H_ind+len_orbitals), (H_ind):(H_ind+len_orbitals)] = onsite_i
             H_ind += len_orbitals
 
 
diff --git a/sys_input.py b/sys_input.py
index cdfdb68..7579a4c 100644
--- a/sys_input.py
+++ b/sys_input.py
@@ -50,5 +50,5 @@ def get_kpts(self):
     sys_input = Sys_input('./input_Jancu_PRB_76_115202_2007.yaml')
     sys = sys_input.system
 
-    print sys.get_soc_mat()
+    print(sys.get_soc_mat())
     # struct = sys.structure
diff --git a/system.py b/system.py
index c261b5b..1816560 100644
--- a/system.py
+++ b/system.py
@@ -117,7 +117,7 @@ def calc_volume(self, atom_i):
         assert len(d_mat) == 4, 'tetrahedron required! # of bond = {}'.format(len(d_mat))
         a, b, c, d = d_mat
         vol = 1/6. * np.linalg.det([a-d, b-d, c-d])
-        print vol
+        print(vol)
 
     def get_onsite_term(self, atom_i):
         """ calc onsite term
@@ -225,7 +225,7 @@ def get_onsite_sd(beta, dir_cos):
         if self.scale_params is None or \
             (not atoms[atom_i].element in self.scale_params or \
              self.scale_params[atoms[atom_i].element] is None):
-            print 'a'
+            print('a')
             e_s = params['e_s']
             if 'px' in  atoms[atom_i].orbitals:
                 e_p = params['e_p']
diff --git a/tb_params.py b/tb_params.py
index e2fef2a..b383463 100644
--- a/tb_params.py
+++ b/tb_params.py
@@ -7,7 +7,7 @@ def get_hop_int(V_sss=0, V_sps=0, V_pps=0, V_ppp=0,
                 V_SSs=0, V_sSs=0, V_Sps=0, V_Sds=0,
                 l=0, m=0, n=0):
 
-    hop_int = [[None for _ in xrange(10)] for __ in xrange(10)]
+    hop_int = [[None for _ in range(10)] for __ in range(10)]
 
     hop_int[0][0] = V_sss
     hop_int[0][1] = l * V_sps
diff --git a/vasp_io.py b/vasp_io.py
index dff1ef5..9ac216a 100644
--- a/vasp_io.py
+++ b/vasp_io.py
@@ -110,8 +110,8 @@ def _parse_kpt(line):
             energy_list = np.array(energy_list).reshape(shape_e)
             K_list = np.array(K_list).reshape(shape_K)
             return kpt_list_prim, k_wt_list_prim, energy_list, K_list, kpt_list
-    except Exception, e:
-        print e
+    except  e:
+        print(e)
         raise e
 
 
@@ -208,7 +208,7 @@ def _parse_proj_phase(line, n_orbits):
             n_kpts, n_bands, n_ions, n_orbits, orbit_names = \
                 _parse_procar_metadata(procar)
 
-            print n_orbits
+            print(n_orbits)
 
             Proj = np.zeros((n_kpts, n_bands, n_ions, n_orbits), float)
             Proj_cmplx = np.zeros((n_kpts, n_bands, n_ions, n_orbits), complex)
@@ -265,10 +265,10 @@ def _parse_proj_phase(line, n_orbits):
             return Kpts, k_wt, Eigs, Proj, Proj_cmplx, Occs
         else:
             return Kpts, k_wt, Eigs, Proj, Occs
-    except Exception, e:
-        print e
-        print line
-        print 'fail to read {}'.format(file_name)
+    except e:
+        print (e)
+        print (line)
+        print ('fail to read {}'.format(file_name))
 
 
 def readPROCAR(fileName='PROCAR', orbital=-1):
@@ -379,7 +379,7 @@ def readCONTCAR(fileName='CONTCAR', rtspecies=False, rt_comment=False):
             if DorC[0]=='D' or  DorC[0]=='d' : # Direct
                 coord = latticeVecs[0]*coord[0]+latticeVecs[1]*coord[1]+latticeVecs[2]*coord[2]
             else: 
-                print "check coord! it's not direct form"
+                print ("check coord! it's not direct form")
 
             atomSet.append([symbol,coord])
         k += 1
@@ -706,7 +706,7 @@ def get_eps(OUTCAR='./OUTCAR'):
         eps = [item for idx, item in enumerate(eps) if idx % 2 == 0]    
         return eps
     except IOError as e: 
-        print "I/O error({0}): {1}".format(e.errno, e.strerror)
+        print ("I/O error({0}): {1}".format(e.errno, e.strerror))
         return None
 
 def readTRANCAR(dir_name, file_name='TRANCAR'):
@@ -833,4 +833,4 @@ def read_stress(dir_name, filre_name='OUTCAR'):
     # readPROCAR_phase(procar_12 + '/PROCAR')
     # readPRJCAR('/home/users/nwan/cj01/00_NW/R3/00_pristine/unfold/bulk/00_222/PRJCAR')
     stress = read_stress('./')
-    print stress
+    print (stress)