diff --git a/blackbody.py b/blackbody.py
index 4cd2b22..6c979bb 100755
--- a/blackbody.py
+++ b/blackbody.py
@@ -67,7 +67,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, numpy, pylab
 
@@ -176,9 +176,9 @@ def figures ():
     blackbody_patch_plot (T_list_cool, 'Cool Blackbody Colors', 'Blackbody-CoolPatch')
 
     # color vs temperature
-    blackbody_color_vs_temperature_plot (range (1200, 16000, 50),   'Blackbody Colors',      'Blackbody-Colors')
-    blackbody_color_vs_temperature_plot (range (10000, 40000, 100), 'Hot Blackbody Colors',  'Blackbody-HotColors')
-    blackbody_color_vs_temperature_plot (range (950, 1200, 1),      'Cool Blackbody Colors', 'Blackbody-CoolColors')
+    blackbody_color_vs_temperature_plot (list(range(1200, 16000, 50)),   'Blackbody Colors',      'Blackbody-Colors')
+    blackbody_color_vs_temperature_plot (list(range(10000, 40000, 100)), 'Hot Blackbody Colors',  'Blackbody-HotColors')
+    blackbody_color_vs_temperature_plot (list(range(950, 1200, 1)),      'Cool Blackbody Colors', 'Blackbody-CoolColors')
 
     # spectrum of specific temperatures
     blackbody_spectrum_plot (2000.0)
diff --git a/ciexyz.py b/ciexyz.py
index c7d460f..dd2b66a 100755
--- a/ciexyz.py
+++ b/ciexyz.py
@@ -116,7 +116,7 @@ def get_normalized_spectral_line_colors (
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, numpy
 
@@ -690,7 +690,7 @@ def empty_spectrum ():
 
     The result can be passed to xyz_from_spectrum() to convert to an xyz color.
     '''
-    wl_nm_range = range (start_wl_nm, end_wl_nm + 1)
+    wl_nm_range = list(range(start_wl_nm, end_wl_nm + 1))
     num_wl = len (wl_nm_range)
     spectrum = numpy.zeros ((num_wl, 2))
     for i in range (0, num_wl):
@@ -742,7 +742,7 @@ def get_normalized_spectral_line_colors (
     dwl_angstroms - Wavelength separation, in angstroms (0.1 nm).  Default 10 A. (1 nm spacing)
     '''
     # get range of wavelengths, in angstroms, so that we can have finer resolution than 1 nm
-    wl_angstrom_range = range (10*start_wl_nm, 10*(end_wl_nm + 1), dwl_angstroms)
+    wl_angstrom_range = list(range(10*start_wl_nm, 10*(end_wl_nm + 1), dwl_angstroms))
     # get total point count
     num_spectral = len (wl_angstrom_range)
     num_points   = num_spectral + num_purples
diff --git a/colormodels.py b/colormodels.py
index e6618dd..eef2ea6 100755
--- a/colormodels.py
+++ b/colormodels.py
@@ -248,7 +248,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, numpy
 
diff --git a/figures.py b/figures.py
index b2f63c2..d02022d 100755
--- a/figures.py
+++ b/figures.py
@@ -42,7 +42,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 from . import (colormodels, ciexyz, illuminants, plots, blackbody,
                rayleigh, thinfilm, misc)
diff --git a/illuminants.py b/illuminants.py
index f8424f3..5a1ca54 100755
--- a/illuminants.py
+++ b/illuminants.py
@@ -88,7 +88,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, numpy
 
diff --git a/misc.py b/misc.py
index ea64bee..e07b43c 100755
--- a/misc.py
+++ b/misc.py
@@ -61,7 +61,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, numpy, pylab
 
diff --git a/plots.py b/plots.py
index 0345749..9e96cc1 100755
--- a/plots.py
+++ b/plots.py
@@ -121,7 +121,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, random
 import numpy, pylab
diff --git a/rayleigh.py b/rayleigh.py
index cc5e785..24f9421 100755
--- a/rayleigh.py
+++ b/rayleigh.py
@@ -62,7 +62,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math
 import numpy, pylab
@@ -160,7 +160,7 @@ def figures ():
         'Rayleigh Scattering by Various Illuminants', 'Rayleigh-PatchVarious')
 
     # color vs illuminant temperature
-    T_list = range (1200, 16000, 50)    # must be integers for range()
+    T_list = list(range(1200, 16000, 50))    # must be integers for range()
     rayleigh_color_vs_illuminant_temperature_plot (T_list, 'Rayleigh Scattering Sky Colors', 'Rayleigh-SkyColors')
 
     # spectra for several illuminants
diff --git a/test.py b/test.py
index b4fc98c..be30ee4 100755
--- a/test.py
+++ b/test.py
@@ -27,7 +27,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 from . import (test_colormodels, test_ciexyz, test_illuminants,
                test_blackbody, test_rayleigh, test_thinfilm)
diff --git a/test_blackbody.py b/test_blackbody.py
index a7bb481..ccff0ab 100755
--- a/test_blackbody.py
+++ b/test_blackbody.py
@@ -22,7 +22,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, random, numpy
 
diff --git a/test_ciexyz.py b/test_ciexyz.py
index d886943..2057954 100755
--- a/test_ciexyz.py
+++ b/test_ciexyz.py
@@ -22,7 +22,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import random
 
diff --git a/test_colormodels.py b/test_colormodels.py
index 9365012..9cea5b1 100755
--- a/test_colormodels.py
+++ b/test_colormodels.py
@@ -22,7 +22,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, random, numpy
 from . import colormodels, ciexyz
diff --git a/test_illuminants.py b/test_illuminants.py
index 2543d9b..33b545e 100755
--- a/test_illuminants.py
+++ b/test_illuminants.py
@@ -22,7 +22,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 from . import illuminants
 
diff --git a/test_rayleigh.py b/test_rayleigh.py
index 6ade594..23a915c 100755
--- a/test_rayleigh.py
+++ b/test_rayleigh.py
@@ -22,7 +22,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import random
 
diff --git a/test_thinfilm.py b/test_thinfilm.py
index 3142769..19bed6f 100755
--- a/test_thinfilm.py
+++ b/test_thinfilm.py
@@ -22,7 +22,7 @@
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import random
 
diff --git a/thinfilm.py b/thinfilm.py
index d0befdd..9f597e1 100755
--- a/thinfilm.py
+++ b/thinfilm.py
@@ -82,7 +82,7 @@ class thin_film (n1, n2, n3, thickness_nm) -
 You should have received a copy of the GNU Lesser General Public License
 along with ColorPy.  If not, see <http://www.gnu.org/licenses/>.
 '''
-from __future__ import division, absolute_import, print_function
+
 
 import math, cmath, numpy
 import pylab
@@ -209,7 +209,7 @@ def thinfilm_spectrum_plot (n1, n2, n3, thickness_nm, illuminant, title, filenam
 def figures ():
     '''Draw some thin film plots.'''
     # simple patch plot
-    thickness_nm_list = range (0, 1000, 10)
+    thickness_nm_list = list(range(0, 1000, 10))
     illuminant = illuminants.get_illuminant_D65()
     illuminants.scale_illuminant (illuminant, 9.50)
     thinfilm_patch_plot (1.500, 1.003, 1.500, thickness_nm_list, illuminant, 'ThinFilm Patch Plot', 'ThinFilm-Patch')
@@ -217,7 +217,7 @@ def figures ():
     # plot the colors of films vs thickness.
     # we scale the illuminant to get a better range of color.
     #thickness_nm_list = range (0, 1000, 2)   # faster
-    thickness_nm_list = range (0, 1000, 1)    # nicer
+    thickness_nm_list = list(range(0, 1000, 1))    # nicer
     # gap in glass/plastic
     illuminant = illuminants.get_illuminant_D65()
     illuminants.scale_illuminant (illuminant, 4.50)