diff --git a/interfaces/cython/cantera/mixmaster/CompositionFrame.py b/interfaces/cython/cantera/mixmaster/CompositionFrame.py
index 8d28a5fa2..b3fbdc3b0 100644
--- a/interfaces/cython/cantera/mixmaster/CompositionFrame.py
+++ b/interfaces/cython/cantera/mixmaster/CompositionFrame.py
@@ -1,7 +1,13 @@
-from Tkinter import *
+import sys
+
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
 from Cantera import *
 
-from SpeciesInfo import SpeciesInfo
+from .SpeciesInfo import SpeciesInfo
 #from KineticsFrame import KineticsFrame
 
 _CUTOFF = 1.e-15
diff --git a/interfaces/cython/cantera/mixmaster/ControlPanel.py b/interfaces/cython/cantera/mixmaster/ControlPanel.py
index b2dc7769c..ae7166b2e 100644
--- a/interfaces/cython/cantera/mixmaster/ControlPanel.py
+++ b/interfaces/cython/cantera/mixmaster/ControlPanel.py
@@ -1,11 +1,20 @@
+from __future__ import print_function
+
 from types import *
-from Tkinter import *
-from ScrolledText import ScrolledText
+
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+    from tkinter.scrolledtext import ScrolledText
+else:
+    from Tkinter import *
+    from ScrolledText import ScrolledText
+
 #import datawindow
 #import filewindow
 
 def ff():
-    print ' hi '
+    print(' hi ')
 
 class ControlWindow(Frame):
     fncs = [ff]*10
@@ -90,23 +99,23 @@ class ControlWindow(Frame):
         return filemenu
 
 def testevent(event):
-    print 'event ',event.value
+    print('event ',event.value)
 
-def make_menu(name, menubar, list):
+def make_menu(name, menubar, lst):
     nc = len(name)
     button=Menubutton(menubar, text=name, width=nc+4, padx=3,pady=1)
     button.pack(side=LEFT)
     menu = Menu(button,tearoff=FALSE)
     m = menu
     i = 0
-    for entry in list:
+    for entry in lst:
         i += 1
         if entry == 'separator':
             menu.add_separator({})
-        elif type(entry)==ListType:
+        elif isinstance(entry, list):
             for num in entry:
                 menu.entryconfig(num,state=DISABLED)
-        elif type(entry[1]) != ListType:
+        elif not isinstance(entry[1], list):
             if i == 20:
                 i = 0
                 submenu = Menu(button,tearoff=FALSE)
@@ -143,7 +152,6 @@ def menuitem_state(button, *statelist):
             pass
 
 class ArgumentWindow(Toplevel):
-    import tkMessageBox
     def __init__(self, sim, **options):
         Toplevel.__init__(self, sim.cwin)
         self.resizable(FALSE,FALSE)
diff --git a/interfaces/cython/cantera/mixmaster/DataFrame.py b/interfaces/cython/cantera/mixmaster/DataFrame.py
index a1aa5118d..1dbfd8c19 100644
--- a/interfaces/cython/cantera/mixmaster/DataFrame.py
+++ b/interfaces/cython/cantera/mixmaster/DataFrame.py
@@ -1,12 +1,18 @@
-import os, math, string
-from Tkinter import *
+import os, math, string, sys
+
+if sys.version_info.major == 3:
+    from tkinter import *
+    from tkinter.filedialog import askopenfilename
+else:
+    from Tkinter import *
+    from tkFileDialog import askopenfilename
+
 from Cantera import *
 from Cantera.num import *
 from Cantera import num
-from tkFileDialog import askopenfilename
-from GraphFrame import Graph
-from DataGraph import DataGraph, plotLimits
-from ControlPanel import make_menu
+from .GraphFrame import Graph
+from .DataGraph import DataGraph, plotLimits
+from .ControlPanel import make_menu
 
 
 U_LOC = 1
@@ -180,7 +186,7 @@ class DataFrame(Frame):
 
         if self.data[P_LOC,0] == 0.0:
             self.data[P_LOC,:] = ones(self.np,'d')*OneAtm
-            print 'Warning: no pressure data. P set to 1 atm.'
+            print('Warning: no pressure data. P set to 1 atm.')
 
         self.sc.config(cnf={'from':0,'to':self.np-1})
         if self.loc.get() <= 0:
diff --git a/interfaces/cython/cantera/mixmaster/DataGraph.py b/interfaces/cython/cantera/mixmaster/DataGraph.py
index 2b4e76a40..ba098cd09 100644
--- a/interfaces/cython/cantera/mixmaster/DataGraph.py
+++ b/interfaces/cython/cantera/mixmaster/DataGraph.py
@@ -1,5 +1,10 @@
+import sys
+
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
 
-from Tkinter import *
 import math
 from Cantera.num import *
 
diff --git a/interfaces/cython/cantera/mixmaster/Edit.py b/interfaces/cython/cantera/mixmaster/Edit.py
index d95b50aae..205856fa6 100644
--- a/interfaces/cython/cantera/mixmaster/Edit.py
+++ b/interfaces/cython/cantera/mixmaster/Edit.py
@@ -1,10 +1,16 @@
-from Tkinter import *
+from __future__ import print_function
+import sys
 
-from ElementFrame import getElements
-from utilities import handleError
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
+from .ElementFrame import getElements
+from .utilities import handleError
 from Cantera import *
-from config import *
-from SpeciesFrame import getSpecies
+from .config import *
+from .SpeciesFrame import getSpecies
 
 def testit():
     pass
@@ -25,7 +31,7 @@ class EditFrame(Frame):
     def __init__(self, master, app):
         Frame.__init__(self, master)
         self.mix = app.mix
-        print self.mix, dir(self.mix)
+        print(self.mix, dir(self.mix))
         self.app = app
         self.master = master
         self.master.title("Cantera Mechanism Editor")
@@ -76,8 +82,8 @@ class EditFrame(Frame):
                 c, r = 0, r + 1
 
     def getspecies(self):
-        print getSpecies(self.mix.speciesNames(),
-                         self.mix.speciesNames())
+        print(getSpecies(self.mix.speciesNames(),
+                         self.mix.speciesNames()))
 
     def editSpecies(self, event=None):
         e = Toplevel(event.widget.master)
@@ -145,7 +151,7 @@ class EditFrame(Frame):
         for fr in e.children.values():
             for item in fr.children.values():
                 try:
-                    print item.cget('selection')
+                    print(item.cget('selection'))
                 except:
                     pass
         e.destroy()
diff --git a/interfaces/cython/cantera/mixmaster/ElementFrame.py b/interfaces/cython/cantera/mixmaster/ElementFrame.py
index e0c0a5ed9..9678c1598 100644
--- a/interfaces/cython/cantera/mixmaster/ElementFrame.py
+++ b/interfaces/cython/cantera/mixmaster/ElementFrame.py
@@ -3,9 +3,13 @@
 #  the selected elements
 #
 
-from Tkinter import *
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
 from types import *
-import tkMessageBox
 import string
 
 from Cantera import *
@@ -140,15 +144,15 @@ class ElementPropertyFrame(Frame):
                                      sticky=W,
                                      padx=10)
             Label(self,
-                  text=`el.atomicNumber`).grid(column=1,
-                                               row=n,
-                                               sticky=W,
-                                               padx=10)
+                  text=repr(el.atomicNumber)).grid(column=1,
+                                                   row=n,
+                                                   sticky=W,
+                                                   padx=10)
             Label(self,
-                  text=`el.atomicWeight`).grid(column=2,
-                                               row=n,
-                                               sticky=W,
-                                               padx=10)
+                  text=repr(el.atomicWeight)).grid(column=2,
+                                                   row=n,
+                                                   sticky=W,
+                                                   padx=10)
             n = n + 1
 
 
@@ -179,4 +183,4 @@ def showElementProperties(ellist):
 
 
 if __name__ == "__main__":
-    print getElements()
+    print(getElements())
diff --git a/interfaces/cython/cantera/mixmaster/GraphFrame.py b/interfaces/cython/cantera/mixmaster/GraphFrame.py
index d473cb41d..e84569a85 100644
--- a/interfaces/cython/cantera/mixmaster/GraphFrame.py
+++ b/interfaces/cython/cantera/mixmaster/GraphFrame.py
@@ -1,5 +1,9 @@
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
 
-from Tkinter import *
 import math
 
 class Graph(Frame):
@@ -59,8 +63,8 @@ class Graph(Frame):
                              relief=SUNKEN,bd=1)
         self.canvas.create_text(4,2,text=self.maxY,anchor=NW)
         self.canvas.create_text(4,self.graph_h,text=self.minY,anchor=SW)
-        self.ml["text"] = `minX`
-        self.mr["text"] = `maxX`
+        self.ml["text"] = repr(minX)
+        self.mr["text"] = repr(maxX)
         self.canvas.pack()
         self.last_points = []
 
@@ -125,4 +129,4 @@ if __name__=='__main__':
     #print("finished")
     g.pauseWhenFinished()
     h.pauseWhenFinished()
-    print g
+    print(g)
diff --git a/interfaces/cython/cantera/mixmaster/ImportFrame.py b/interfaces/cython/cantera/mixmaster/ImportFrame.py
index 6208aa197..904508705 100644
--- a/interfaces/cython/cantera/mixmaster/ImportFrame.py
+++ b/interfaces/cython/cantera/mixmaster/ImportFrame.py
@@ -1,8 +1,14 @@
-import os, math
-from Tkinter import *
+import os, math,sys
+
+if sys.version_info.major == 3:
+    from tkinter import *
+    from tkinter.filedialog import askopenfilename
+else:
+    from Tkinter import *
+    from tkFileDialog import askopenfilename
+
 from Cantera import *
 #from Cantera.ck2ctml import ck2ctml
-from tkFileDialog import askopenfilename
 
 class ImportFrame(Frame):
     def __init__(self,top):
@@ -84,7 +90,7 @@ class ImportFrame(Frame):
         else: nm = ff
         outfile = p+os.sep+nm+'.xml'
         try:
-            print 'not supported.'
+            print('not supported.')
             #ck2ctml(infile = ckfile, thermo = thermdb,
             #       transport = trandb, outfile = outfile,
             #       id = nm)
@@ -92,7 +98,7 @@ class ImportFrame(Frame):
             return
 
         except:
-            print 'Errors were encountered. See log file ck2ctml.log'
+            print('Errors were encountered. See log file ck2ctml.log')
             self.hide()
             return
 
diff --git a/interfaces/cython/cantera/mixmaster/KineticsFrame.py b/interfaces/cython/cantera/mixmaster/KineticsFrame.py
index 80728b72d..40a777426 100644
--- a/interfaces/cython/cantera/mixmaster/KineticsFrame.py
+++ b/interfaces/cython/cantera/mixmaster/KineticsFrame.py
@@ -1,8 +1,15 @@
-import os, math
-from Tkinter import *
+from __future__ import print_function
+
+import os, math, sys
+
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
 from Cantera import *
 
-from SpeciesInfo import SpeciesInfo
+from .SpeciesInfo import SpeciesInfo
 from Cantera import rxnpath
 import webbrowser
 
@@ -241,7 +248,7 @@ class ReactionKineticsFrame(Frame):
 
     def show(self,e=None,b=None,c=None):
         v = self.vis.get()
-        print e,b,c
+        print(e,b,c)
         #if v == 0:
         #       self.hide()
         #       return
diff --git a/interfaces/cython/cantera/mixmaster/MechManager.py b/interfaces/cython/cantera/mixmaster/MechManager.py
index 7a1843f0c..9e0135100 100644
--- a/interfaces/cython/cantera/mixmaster/MechManager.py
+++ b/interfaces/cython/cantera/mixmaster/MechManager.py
@@ -1,7 +1,13 @@
 from Cantera import *
-from Tkinter import *
-from ControlPanel import ControlWindow
-from ControlPanel import make_menu, menuitem_state
+
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
+from .ControlPanel import ControlWindow
+from .ControlPanel import make_menu, menuitem_state
 #from Cantera.Examples.Tk import _mechdir
 import os
 
diff --git a/interfaces/cython/cantera/mixmaster/Mix.py b/interfaces/cython/cantera/mixmaster/Mix.py
index b0b95317f..0d6ee9aaa 100644
--- a/interfaces/cython/cantera/mixmaster/Mix.py
+++ b/interfaces/cython/cantera/mixmaster/Mix.py
@@ -1,6 +1,6 @@
 from Cantera import GasConstant, OneAtm
 from Cantera.num import zeros, ones
-from utilities import handleError
+from .utilities import handleError
 
 def spdict(phase, x):
     nm = phase.speciesNames()
diff --git a/interfaces/cython/cantera/mixmaster/NewFlowFrame.py b/interfaces/cython/cantera/mixmaster/NewFlowFrame.py
index 0ac5791a6..7c14c06b2 100644
--- a/interfaces/cython/cantera/mixmaster/NewFlowFrame.py
+++ b/interfaces/cython/cantera/mixmaster/NewFlowFrame.py
@@ -1,7 +1,12 @@
-from Tkinter import *
 from Cantera import *
 
-from SpeciesInfo import SpeciesInfo
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
+from .SpeciesInfo import SpeciesInfo
 
 _CUTOFF = 1.e-15
 _ATOL = 1.e-15
diff --git a/interfaces/cython/cantera/mixmaster/SpeciesFrame.py b/interfaces/cython/cantera/mixmaster/SpeciesFrame.py
index 8b0ee0765..b514617c2 100644
--- a/interfaces/cython/cantera/mixmaster/SpeciesFrame.py
+++ b/interfaces/cython/cantera/mixmaster/SpeciesFrame.py
@@ -3,10 +3,13 @@
 #  the selected elements
 #
 
-from Tkinter import *
-from types import *
-import tkMessageBox
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
 
+from types import *
 from Cantera import *
 
 class SpeciesFrame(Frame):
@@ -171,4 +174,4 @@ def showElementProperties(ellist):
 
 
 if __name__ == "__main__":
-    print getSpecies()
+    print(getSpecies())
diff --git a/interfaces/cython/cantera/mixmaster/SpeciesInfo.py b/interfaces/cython/cantera/mixmaster/SpeciesInfo.py
index 5eff48a4c..92668036f 100644
--- a/interfaces/cython/cantera/mixmaster/SpeciesInfo.py
+++ b/interfaces/cython/cantera/mixmaster/SpeciesInfo.py
@@ -1,9 +1,14 @@
-from Tkinter import *
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
 import re, math
 from Cantera import *
-from Units import temperature, specificEnergy, specificEntropy
-from UnitChooser import UnitVar
-from GraphFrame import Graph
+from .Units import temperature, specificEnergy, specificEntropy
+from .UnitChooser import UnitVar
+from .GraphFrame import Graph
 
 def testit():
     pass
@@ -44,7 +49,7 @@ class SpeciesInfo(Label):
         Label(self.eframe,text='Atoms:')\
                                .grid(row=0,column=0,sticky=N+W)
         for el, c in self.sp.composition():
-            Label(self.eframe,text=`int(c)`+' '+el).grid(row=0,column=r)
+            Label(self.eframe,text=repr(int(c))+' '+el).grid(row=0,column=r)
             r = r + 1
 
 
diff --git a/interfaces/cython/cantera/mixmaster/ThermoFrame.py b/interfaces/cython/cantera/mixmaster/ThermoFrame.py
index fbc42606b..f4170b747 100644
--- a/interfaces/cython/cantera/mixmaster/ThermoFrame.py
+++ b/interfaces/cython/cantera/mixmaster/ThermoFrame.py
@@ -1,12 +1,17 @@
 
 
 from Cantera import *
-from Tkinter import *
 
-from Units import temperature, pressure, density, specificEnergy, specificEntropy
-from UnitChooser import UnitVar
-from ThermoProp import ThermoProp
-from utilities import handleError
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
+from .Units import temperature, pressure, density, specificEnergy, specificEntropy
+from .UnitChooser import UnitVar
+from .ThermoProp import ThermoProp
+from .utilities import handleError
 
 _PRESSURE = 1
 _TEMPERATURE = 0
diff --git a/interfaces/cython/cantera/mixmaster/ThermoProp.py b/interfaces/cython/cantera/mixmaster/ThermoProp.py
index bd37ffd5f..b37d1922f 100644
--- a/interfaces/cython/cantera/mixmaster/ThermoProp.py
+++ b/interfaces/cython/cantera/mixmaster/ThermoProp.py
@@ -1,5 +1,10 @@
-from Tkinter import *
-from UnitChooser import UnitVar
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
+from .UnitChooser import UnitVar
 
 _tv = ['Temperature','Internal Energy','Enthalpy']
 _pv = ['Pressure', 'Density']
diff --git a/interfaces/cython/cantera/mixmaster/TransportFrame.py b/interfaces/cython/cantera/mixmaster/TransportFrame.py
index 29473754a..38a8c8212 100644
--- a/interfaces/cython/cantera/mixmaster/TransportFrame.py
+++ b/interfaces/cython/cantera/mixmaster/TransportFrame.py
@@ -1,4 +1,8 @@
-from Tkinter import *
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
 
 class TransportFrame(Frame):
     def show(self, i, frame, row, col):
diff --git a/interfaces/cython/cantera/mixmaster/UnitChooser.py b/interfaces/cython/cantera/mixmaster/UnitChooser.py
index 17bcb97eb..602007b96 100644
--- a/interfaces/cython/cantera/mixmaster/UnitChooser.py
+++ b/interfaces/cython/cantera/mixmaster/UnitChooser.py
@@ -1,4 +1,9 @@
-from Tkinter import *
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
+
 import re
 
 class UnitVar(Frame):
diff --git a/interfaces/cython/cantera/mixmaster/Units/SI.py b/interfaces/cython/cantera/mixmaster/Units/SI.py
index a363b248a..29a0c5e3f 100644
--- a/interfaces/cython/cantera/mixmaster/Units/SI.py
+++ b/interfaces/cython/cantera/mixmaster/Units/SI.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env python
-from unit import unit, dimensionless
+from .unit import unit, dimensionless
 
 #
 # The basic SI units
@@ -75,39 +75,39 @@ yocto = 1e-24
 
 if __name__ == "__main__":
 
-    print "The 7 base SI units:"
-    print "             meter: %s" % meter
-    print "          kilogram: %s" % kilogram
-    print "            second: %s" % second
-    print "            ampere: %s" % ampere
-    print "            kelvin: %s" % kelvin
-    print "              mole: %s" % mole
-    print "           candela: %s" % candela
-    print
-    print "The 21 SI derived units with special names:"
-    print "            radian: %s" % radian
-    print "         steradian: %s" % steradian
-    print "             hertz: %s" % hertz
+    print("The 7 base SI units:")
+    print("             meter: %s" % meter)
+    print("          kilogram: %s" % kilogram)
+    print("            second: %s" % second)
+    print("            ampere: %s" % ampere)
+    print("            kelvin: %s" % kelvin)
+    print("              mole: %s" % mole)
+    print("           candela: %s" % candela)
+    print("")
+    print("The 21 SI derived units with special names:")
+    print("            radian: %s" % radian)
+    print("         steradian: %s" % steradian)
+    print("             hertz: %s" % hertz)
 
-    print "            newton: %s" % newton
-    print "            pascal: %s" % pascal
-    print "             joule: %s" % joule
-    print "              watt: %s" % watt
+    print("            newton: %s" % newton)
+    print("            pascal: %s" % pascal)
+    print("             joule: %s" % joule)
+    print("              watt: %s" % watt)
 
-    print "           coulomb: %s" % coulomb
-    print "              volt: %s" % volt
-    print "             farad: %s" % farad
-    print "               ohm: %s" % ohm
-    print "           siemens: %s" % siemens
-    print "             weber: %s" % weber
-    print "             tesla: %s" % tesla
-    print "             henry: %s" % henry
+    print("           coulomb: %s" % coulomb)
+    print("              volt: %s" % volt)
+    print("             farad: %s" % farad)
+    print("               ohm: %s" % ohm)
+    print("           siemens: %s" % siemens)
+    print("             weber: %s" % weber)
+    print("             tesla: %s" % tesla)
+    print("             henry: %s" % henry)
 
-    print "    degree Celsius: %s" % celsius
+    print("    degree Celsius: %s" % celsius)
 
-    print "             lumen: %s" % lumen
-    print "               lux: %s" % lux
+    print("             lumen: %s" % lumen)
+    print("               lux: %s" % lux)
 
-    print "         becquerel: %s" % becquerel
-    print "              gray: %s" % gray
-    print "           sievert: %s" % sievert
+    print("         becquerel: %s" % becquerel)
+    print("              gray: %s" % gray)
+    print("           sievert: %s" % sievert)
diff --git a/interfaces/cython/cantera/mixmaster/Units/density.py b/interfaces/cython/cantera/mixmaster/Units/density.py
index ef89cbbe7..ea8ce6dda 100644
--- a/interfaces/cython/cantera/mixmaster/Units/density.py
+++ b/interfaces/cython/cantera/mixmaster/Units/density.py
@@ -1,4 +1,5 @@
-import SI, math
+import math
+from . import SI
 
 #
 # Definitions of common density units
diff --git a/interfaces/cython/cantera/mixmaster/Units/energy.py b/interfaces/cython/cantera/mixmaster/Units/energy.py
index 7f7d2f084..247500ee3 100644
--- a/interfaces/cython/cantera/mixmaster/Units/energy.py
+++ b/interfaces/cython/cantera/mixmaster/Units/energy.py
@@ -1,4 +1,4 @@
-from SI import joule
+from .SI import joule
 
 #
 # Definitions of common energy units
diff --git a/interfaces/cython/cantera/mixmaster/Units/force.py b/interfaces/cython/cantera/mixmaster/Units/force.py
index 6a9a6bdbc..5b36f6846 100644
--- a/interfaces/cython/cantera/mixmaster/Units/force.py
+++ b/interfaces/cython/cantera/mixmaster/Units/force.py
@@ -1,4 +1,4 @@
-from SI import meter
+from .SI import meter
 
 #
 # Definitions of common force units
diff --git a/interfaces/cython/cantera/mixmaster/Units/length.py b/interfaces/cython/cantera/mixmaster/Units/length.py
index 37c58228a..ae025a95a 100644
--- a/interfaces/cython/cantera/mixmaster/Units/length.py
+++ b/interfaces/cython/cantera/mixmaster/Units/length.py
@@ -1,5 +1,5 @@
-from SI import meter
-from SI import nano, milli, centi, kilo
+from .SI import meter
+from .SI import nano, milli, centi, kilo
 
 #
 # Definitions of common length units
diff --git a/interfaces/cython/cantera/mixmaster/Units/mass.py b/interfaces/cython/cantera/mixmaster/Units/mass.py
index 35451f4da..8b4e01d1d 100644
--- a/interfaces/cython/cantera/mixmaster/Units/mass.py
+++ b/interfaces/cython/cantera/mixmaster/Units/mass.py
@@ -1,4 +1,4 @@
-from SI import kilogram
+from .SI import kilogram
 
 #
 # Definitions of common mass units
diff --git a/interfaces/cython/cantera/mixmaster/Units/power.py b/interfaces/cython/cantera/mixmaster/Units/power.py
index 2fac3b872..b8228575c 100644
--- a/interfaces/cython/cantera/mixmaster/Units/power.py
+++ b/interfaces/cython/cantera/mixmaster/Units/power.py
@@ -1,4 +1,4 @@
-from SI import watt, kilo
+from .SI import watt, kilo
 
 #
 # Definitions of common power units
diff --git a/interfaces/cython/cantera/mixmaster/Units/pressure.py b/interfaces/cython/cantera/mixmaster/Units/pressure.py
index 35397006f..5c80c34ff 100644
--- a/interfaces/cython/cantera/mixmaster/Units/pressure.py
+++ b/interfaces/cython/cantera/mixmaster/Units/pressure.py
@@ -1,4 +1,4 @@
-import SI
+from . import SI
 
 #
 # Definitions of common pressure units
diff --git a/interfaces/cython/cantera/mixmaster/Units/specificEnergy.py b/interfaces/cython/cantera/mixmaster/Units/specificEnergy.py
index 1adde01c9..f0dfc8dec 100644
--- a/interfaces/cython/cantera/mixmaster/Units/specificEnergy.py
+++ b/interfaces/cython/cantera/mixmaster/Units/specificEnergy.py
@@ -1,4 +1,4 @@
-import SI, energy, mass
+from . import SI, energy, mass
 
 #
 # Definitions of common energy units
diff --git a/interfaces/cython/cantera/mixmaster/Units/specificEntropy.py b/interfaces/cython/cantera/mixmaster/Units/specificEntropy.py
index ab8204a2c..046a498d8 100644
--- a/interfaces/cython/cantera/mixmaster/Units/specificEntropy.py
+++ b/interfaces/cython/cantera/mixmaster/Units/specificEntropy.py
@@ -1,4 +1,4 @@
-import SI, energy, mass
+from . import SI, energy, mass
 
 units = ['J__kg_K', 'kJ__kg_K', 'cal__g_K']
 
diff --git a/interfaces/cython/cantera/mixmaster/Units/speed.py b/interfaces/cython/cantera/mixmaster/Units/speed.py
index ca32bd62e..93374c83a 100644
--- a/interfaces/cython/cantera/mixmaster/Units/speed.py
+++ b/interfaces/cython/cantera/mixmaster/Units/speed.py
@@ -1,5 +1,5 @@
-from time import hour
-from length import nautical_mile
+from .time import hour
+from .length import nautical_mile
 
 #
 # Definitions of common speed units
diff --git a/interfaces/cython/cantera/mixmaster/Units/temperature.py b/interfaces/cython/cantera/mixmaster/Units/temperature.py
index d4339a118..865070d45 100644
--- a/interfaces/cython/cantera/mixmaster/Units/temperature.py
+++ b/interfaces/cython/cantera/mixmaster/Units/temperature.py
@@ -1,4 +1,4 @@
-import SI
+from . import SI
 
 K = SI.kelvin
 R = (9.0/5.0)*K
diff --git a/interfaces/cython/cantera/mixmaster/Units/time.py b/interfaces/cython/cantera/mixmaster/Units/time.py
index 3b96a9e0c..b7f980fb2 100644
--- a/interfaces/cython/cantera/mixmaster/Units/time.py
+++ b/interfaces/cython/cantera/mixmaster/Units/time.py
@@ -1,4 +1,4 @@
-from SI import second
+from .SI import second
 
 #
 # Definitions of common time units
diff --git a/interfaces/cython/cantera/mixmaster/Units/unit.py b/interfaces/cython/cantera/mixmaster/Units/unit.py
index 427192a85..b8096a168 100644
--- a/interfaces/cython/cantera/mixmaster/Units/unit.py
+++ b/interfaces/cython/cantera/mixmaster/Units/unit.py
@@ -1,6 +1,6 @@
 import operator
 
-class unit:
+class unit(object):
 
     _zero = (0,) * 7
     _negativeOne = (-1, ) * 7
@@ -37,8 +37,10 @@ class unit:
 
         return unit(value, derivation)
 
-
     def __div__(self, other):
+        return self.__truediv__(other)
+
+    def __truediv__(self, other):
         if type(other) == type(0) or type(other) == type(0.0):
             return unit(self.value/other, self.derivation)
 
@@ -77,6 +79,9 @@ class unit:
         return unit.__mul__(self, other)
 
     def __rdiv__(self, other):
+        return self.__rtruediv__(other)
+
+    def __rtruediv__(self, other):
         if type(other) != type(0) and type(other) != type(0.0):
             raise BadOperation(self, other)
 
diff --git a/interfaces/cython/cantera/mixmaster/Units/volume.py b/interfaces/cython/cantera/mixmaster/Units/volume.py
index 8c491eca3..c614c8ee4 100644
--- a/interfaces/cython/cantera/mixmaster/Units/volume.py
+++ b/interfaces/cython/cantera/mixmaster/Units/volume.py
@@ -1,4 +1,4 @@
-from length import meter, centimeter, foot, inch
+from .length import meter, centimeter, foot, inch
 
 #
 # Definitions of common volume units
diff --git a/interfaces/cython/cantera/mixmaster/__init__.py b/interfaces/cython/cantera/mixmaster/__init__.py
index 58c70d95b..f8b58374a 100644
--- a/interfaces/cython/cantera/mixmaster/__init__.py
+++ b/interfaces/cython/cantera/mixmaster/__init__.py
@@ -1,4 +1,4 @@
 
 # from Cantera import *
 
-from main import MixMaster
+#from .main import MixMaster
diff --git a/interfaces/cython/cantera/mixmaster/flowpanel.py b/interfaces/cython/cantera/mixmaster/flowpanel.py
index 4efdfcf92..dde60c79e 100644
--- a/interfaces/cython/cantera/mixmaster/flowpanel.py
+++ b/interfaces/cython/cantera/mixmaster/flowpanel.py
@@ -1,7 +1,11 @@
 
 
 # functionality imports
-from Tkinter import *
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
 
 from Cantera.gui import menu, newflow
 
@@ -27,7 +31,7 @@ class App:
         self.newbutton.grid(row = 1, column = 1)
 
     def notyet(self):
-        print 'not yet!'
+        print('not yet!')
 
 
     def newflow(self):
diff --git a/interfaces/cython/cantera/mixmaster/main.py b/interfaces/cython/cantera/mixmaster/main.py
index 434cd8ee2..f1f3e61ee 100644
--- a/interfaces/cython/cantera/mixmaster/main.py
+++ b/interfaces/cython/cantera/mixmaster/main.py
@@ -10,29 +10,37 @@ _app_version = '1.0'
 
 
 # functionality imports
-from Tkinter import *
-import tkMessageBox
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+    from tkinter import messagebox
+    from tkinter.filedialog import askopenfilename
+else:
+    from Tkinter import *
+    import tkMessageBox as messagebox
+    from tkFileDialog import askopenfilename
+
 import sys, os, string
 
 # Cantera imports
 from Cantera import *
 from Cantera.num import zeros
-import utilities
 from Cantera.gases import IdealGasMix
+from . import utilities
 
 # local imports
-from TransportFrame import TransportFrame
-from CompositionFrame import MixtureFrame
-from ThermoFrame import ThermoFrame
-from ImportFrame import ImportFrame
-from DataFrame import DataFrame
-from KineticsFrame import SpeciesKineticsFrame, ReactionKineticsFrame, ReactionPathFrame
+from .TransportFrame import TransportFrame
+from .CompositionFrame import MixtureFrame
+from .ThermoFrame import ThermoFrame
+from .ImportFrame import ImportFrame
+from .DataFrame import DataFrame
+from .KineticsFrame import SpeciesKineticsFrame, ReactionKineticsFrame, ReactionPathFrame
 #from Edit import EditFrame
-from MechManager import MechManager, _autoload
-from UnitChooser import UnitVar
-from ControlPanel import ControlWindow
-from ControlPanel import make_menu, menuitem_state
-from Mix import Mix, Species
+from .MechManager import MechManager, _autoload
+from .UnitChooser import UnitVar
+from .ControlPanel import ControlWindow
+from .ControlPanel import make_menu, menuitem_state
+from .Mix import Mix, Species
 
 def testit():
     return
@@ -44,7 +52,6 @@ class MixMaster:
         sys.exit(0)
 
     def openmech(self):
-        from tkFileDialog import askopenfilename
         pathname = askopenfilename(filetypes=[("Cantera Input Files", "*.cti"),
                                               ("XML Files", "*.xml *.ctml"),
                                               ("All Files", "*.*")])
@@ -81,7 +88,7 @@ class MixMaster:
     def addWindow(self, name, w):
         """Add a new window, or replace an existing one."""
         wstate = ''
-        if self._windows.has_key(name):
+        if name in self._windows:
             try:
                 wstate = self._windows[name].master.state()
                 self._windows[name].master.destroy()
@@ -304,8 +311,8 @@ class MixMaster:
 
     def aboutmix(self):
 
-        m = tkMessageBox.showinfo(title = 'About MixMaster',
-                                  message = """
+        m = messagebox.showinfo(title = 'About MixMaster',
+                                message = """
                      MixMaster
 
                     version """+_app_version+"""
diff --git a/interfaces/cython/cantera/mixmaster/menu.py b/interfaces/cython/cantera/mixmaster/menu.py
index 569c9e881..904f93f87 100644
--- a/interfaces/cython/cantera/mixmaster/menu.py
+++ b/interfaces/cython/cantera/mixmaster/menu.py
@@ -1,17 +1,20 @@
-from Tkinter import *
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+else:
+    from Tkinter import *
 
-def make_menu(name, menubar, list):
-    from types import *
+def make_menu(name, menubar, lst):
     button=Menubutton(menubar, text=name, padx=3,pady=1)
     button.pack(side=LEFT, anchor=W)
     menu = Menu(button,tearoff=FALSE)
-    for entry in list:
+    for entry in lst:
         if entry == 'separator':
             menu.add_separator({})
-        elif type(entry)==ListType:
+        elif isinstance(entry, list):
             for num in entry:
                 menu.entryconfig(num,state=DISABLED)
-        elif type(entry[1]) != ListType:
+        elif not isinstance(entry[1], list):
             if len(entry) == 2 or entry[2] == 'command':
                 menu.add_command(label=entry[0],
                                  command=entry[1])
diff --git a/interfaces/cython/cantera/mixmaster/newflow.py b/interfaces/cython/cantera/mixmaster/newflow.py
index 2da711a20..78defa2ad 100644
--- a/interfaces/cython/cantera/mixmaster/newflow.py
+++ b/interfaces/cython/cantera/mixmaster/newflow.py
@@ -1,7 +1,15 @@
 
-from Tkinter import *
-from tkFileDialog import askopenfilename
-import tkMessageBox
+import sys
+if sys.version_info.major == 3:
+    from tkinter import *
+    from tkinter.filedialog import askopenfilename
+    from tkinter import messagebox
+else:
+    from Tkinter import *
+    import tkMessageBox as messagebox
+    from tkFileDialog import askopenfilename
+
+
 
 from Cantera.gases import IdealGasMix
 from Cantera import *
@@ -104,8 +112,8 @@ class NewFlowDialog:
                 self.gas = IdealGasMix(import_file = infile)
 
         except:
-            tkMessageBox.showerror('Create Gas',
-                                   'Error reading file %s. See log file for more information.' % infile)
+            messagebox.showerror('Create Gas',
+                                 'Error reading file %s. See log file for more information.' % infile)
 
         #self.flow = Flow1D(flow_type = ftype, flow_geom = fgeom,
         #                   pressure = p, grid = gr, gas = g)
diff --git a/interfaces/cython/cantera/mixmaster/utilities.py b/interfaces/cython/cantera/mixmaster/utilities.py
index f498520c1..e2a07fcc3 100644
--- a/interfaces/cython/cantera/mixmaster/utilities.py
+++ b/interfaces/cython/cantera/mixmaster/utilities.py
@@ -3,8 +3,12 @@ import os, sys
 import types, traceback
 
 try:
-    from Tkinter import Tk
-    import tkMessageBox
+    if sys.version_info.major == 3:
+        from tkinter import Tk
+        from tkinter import messagebox
+    else:
+        from Tkinter import Tk
+        import tkMessageBox
     _hasTk = 1
 except:
     _hasTk = 0
@@ -13,14 +17,14 @@ except:
 def write_CSV(f,x):
     """write list x to file f in comma-separated-value format."""
     for e in x:
-        f.write( `e`+',')
+        f.write( repr(e)+',')
     f.write('\n')
 
 
 def _print_value(name, value, unitstr):
-    print string.rjust(name, 15)+  \
+    print(string.rjust(name, 15)+  \
           string.rjust('%10.5e' %value, 15) + ' ' + \
-          string.ljust(unitstr,5),
+          string.ljust(unitstr,5))
 
 def hasTk():
     try:
@@ -32,8 +36,8 @@ def hasTk():
 def handleError(message = '<error>', window = None,
                 fatal = 0, warning = 0, options = None):
     if warning:
-        tkMessageBox.showwarning(title = 'Warning', message = message,
-                                 parent = window)
+        messagebox.showwarning(title = 'Warning', message = message,
+                               parent = window)
     else:
-        m = tkMessageBox.showerror(title = 'Error', message = message,
-                                   parent = window)
+        m = messagebox.showerror(title = 'Error', message = message,
+                                 parent = window)