diff --git a/src/bdump.py b/src/bdump.py
index 9f680c3..8032f58 100644
--- a/src/bdump.py
+++ b/src/bdump.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, subprocess, re, glob, types
 import functools
 from os import popen
diff --git a/src/cfg.py b/src/cfg.py
index 4c17579..020dc1e 100644
--- a/src/cfg.py
+++ b/src/cfg.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys
 
 oneline = "Convert LAMMPS snapshots to AtomEye CFG format"
diff --git a/src/clog.py b/src/clog.py
index abe6440..d26275c 100644
--- a/src/clog.py
+++ b/src/clog.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, re, glob
 from os import popen
 
diff --git a/src/data.py b/src/data.py
index a830bf9..60e8cfd 100644
--- a/src/data.py
+++ b/src/data.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 from os import popen
 
 oneline = "Read, write, manipulate LAMMPS data files"
diff --git a/src/dump.py b/src/dump.py
index 9a853f7..1f1ac25 100644
--- a/src/dump.py
+++ b/src/dump.py
@@ -10,6 +10,7 @@
 
 # Imports and external programs
 
+from __future__ import print_function, absolute_import
 import sys, subprocess, re, glob, types
 from os import popen
 from math import *             # any function could be used by set()
diff --git a/src/ensight.py b/src/ensight.py
index 82b12e1..cc52ec5 100644
--- a/src/ensight.py
+++ b/src/ensight.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, types
 
 oneline = "Convert LAMMPS snapshots or meshes to Ensight format"
diff --git a/src/gl.py b/src/gl.py
index cd1f91a..28057b6 100644
--- a/src/gl.py
+++ b/src/gl.py
@@ -10,6 +10,8 @@
 
 # Imports and external programs
 
+from __future__ import absolute_import
+
 from math import sin,cos,sqrt,pi,acos
 from OpenGL.Tk import *
 from OpenGL.GLUT import *
diff --git a/src/image.py b/src/image.py
index ac3e53f..d664f1f 100644
--- a/src/image.py
+++ b/src/image.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, os, subprocess, re, glob
 from math import *
 try:
diff --git a/src/ldump.py b/src/ldump.py
index 23f75f3..da5b559 100644
--- a/src/ldump.py
+++ b/src/ldump.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, subprocess, re, glob, types
 import functools
 from os import popen
diff --git a/src/log.py b/src/log.py
index 02f8969..6d531f3 100644
--- a/src/log.py
+++ b/src/log.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, re, glob
 import functools
 from os import popen
diff --git a/src/mdump.py b/src/mdump.py
index 1428c23..5a132fe 100644
--- a/src/mdump.py
+++ b/src/mdump.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, subprocess, re, glob, types
 import functools
 from os import popen
diff --git a/src/pdbfile.py b/src/pdbfile.py
index fb7e3e4..7dd0520 100644
--- a/src/pdbfile.py
+++ b/src/pdbfile.py
@@ -10,8 +10,12 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
-import sys, types, glob, urllib.request, urllib.parse, urllib.error
+from __future__ import print_function, absolute_import
+import sys, types, glob
+try:
+  import urllib.request, urllib.parse, urllib.error
+except ImportError:
+  import urllib
 
 oneline = "Read, write PDB files in combo with LAMMPS snapshots"
 
diff --git a/src/pizza.py b/src/pizza.py
index 78c5d8d..7831646 100755
--- a/src/pizza.py
+++ b/src/pizza.py
@@ -17,7 +17,7 @@
 
 # modules needed by pizza.py
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, subprocess, os, string, glob, re
 import time
 
diff --git a/src/rasmol.py b/src/rasmol.py
index 676b7b9..e440046 100644
--- a/src/rasmol.py
+++ b/src/rasmol.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, os, subprocess, re, types
 from pdbfile import pdbfile
 
diff --git a/src/raster.py b/src/raster.py
index 47294bb..d67cbbf 100644
--- a/src/raster.py
+++ b/src/raster.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, os, subprocess, re
 from vizinfo import vizinfo
 from math import fabs,atan,cos,sin
diff --git a/src/svg.py b/src/svg.py
index 8af3ee7..6ddf3f9 100644
--- a/src/svg.py
+++ b/src/svg.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, os, subprocess, re
 import functools
 from vizinfo import vizinfo
diff --git a/src/tdump.py b/src/tdump.py
index 3087760..387e89d 100644
--- a/src/tdump.py
+++ b/src/tdump.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys, subprocess, re, glob, types
 import functools
 from math import sqrt
diff --git a/src/vec.py b/src/vec.py
index abc11fb..181382d 100644
--- a/src/vec.py
+++ b/src/vec.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import types
 
 oneline = "Create numeric vectors from columns in file or list of vecs"
diff --git a/src/vtk.py b/src/vtk.py
index fa26b98..96c2dc7 100644
--- a/src/vtk.py
+++ b/src/vtk.py
@@ -8,6 +8,9 @@
 
 # vtk tool
 
+from __future__ import print_function, absolute_import
+import sys, re
+
 oneline = "Convert LAMMPS snapshots to VTK format"
 
 docstr = """
@@ -34,8 +37,6 @@ v.single(N,"file")      write snapshot for timestep N to file.vtk
 
 # Imports and external programs
 
-import sys, re
-
 # Class definition
 
 class vtk:
diff --git a/src/xyz.py b/src/xyz.py
index ea35ff8..64c70fa 100644
--- a/src/xyz.py
+++ b/src/xyz.py
@@ -10,7 +10,7 @@
 
 # Imports and external programs
 
-from __future__ import absolute_import
+from __future__ import print_function, absolute_import
 import sys
 oneline = "Convert LAMMPS snapshots to XYZ format"