diff --git a/doc/sphinx/conf.py b/doc/sphinx/conf.py
index 6584cce91..3c2e00e87 100644
--- a/doc/sphinx/conf.py
+++ b/doc/sphinx/conf.py
@@ -16,7 +16,7 @@ import sys, os
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     sys.path.insert(0, os.path.abspath('../../build/python3'))
 else:
     sys.path.insert(0, os.path.abspath('../../build/python2'))
@@ -90,7 +90,7 @@ release = '2.1a1'
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 exclude_patterns = []
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     exclude_patterns.append('python/*')
 
 
diff --git a/interfaces/cython/cantera/mixmaster/CompositionFrame.py b/interfaces/cython/cantera/mixmaster/CompositionFrame.py
index b2db479f7..81d5245b5 100644
--- a/interfaces/cython/cantera/mixmaster/CompositionFrame.py
+++ b/interfaces/cython/cantera/mixmaster/CompositionFrame.py
@@ -1,6 +1,6 @@
 import sys
 
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/ControlPanel.py b/interfaces/cython/cantera/mixmaster/ControlPanel.py
index ae7166b2e..9eca455ac 100644
--- a/interfaces/cython/cantera/mixmaster/ControlPanel.py
+++ b/interfaces/cython/cantera/mixmaster/ControlPanel.py
@@ -3,7 +3,7 @@ from __future__ import print_function
 from types import *
 
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
     from tkinter.scrolledtext import ScrolledText
 else:
diff --git a/interfaces/cython/cantera/mixmaster/DataFrame.py b/interfaces/cython/cantera/mixmaster/DataFrame.py
index a51cf3bcd..902bb3a04 100644
--- a/interfaces/cython/cantera/mixmaster/DataFrame.py
+++ b/interfaces/cython/cantera/mixmaster/DataFrame.py
@@ -1,6 +1,6 @@
 import os, math, string, sys
 
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
     from tkinter.filedialog import askopenfilename
 else:
diff --git a/interfaces/cython/cantera/mixmaster/DataGraph.py b/interfaces/cython/cantera/mixmaster/DataGraph.py
index 0e314c9bc..e625e5210 100644
--- a/interfaces/cython/cantera/mixmaster/DataGraph.py
+++ b/interfaces/cython/cantera/mixmaster/DataGraph.py
@@ -1,6 +1,6 @@
 import sys
 
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/Edit.py b/interfaces/cython/cantera/mixmaster/Edit.py
index c56bc3af2..bc9f92a52 100644
--- a/interfaces/cython/cantera/mixmaster/Edit.py
+++ b/interfaces/cython/cantera/mixmaster/Edit.py
@@ -1,7 +1,7 @@
 from __future__ import print_function
 import sys
 
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/ElementFrame.py b/interfaces/cython/cantera/mixmaster/ElementFrame.py
index 1025f3e71..4fc406917 100644
--- a/interfaces/cython/cantera/mixmaster/ElementFrame.py
+++ b/interfaces/cython/cantera/mixmaster/ElementFrame.py
@@ -4,7 +4,7 @@
 #
 
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/GraphFrame.py b/interfaces/cython/cantera/mixmaster/GraphFrame.py
index e84569a85..5be24bd48 100644
--- a/interfaces/cython/cantera/mixmaster/GraphFrame.py
+++ b/interfaces/cython/cantera/mixmaster/GraphFrame.py
@@ -1,5 +1,5 @@
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/ImportFrame.py b/interfaces/cython/cantera/mixmaster/ImportFrame.py
index 3a8d1fdeb..1d1b2a76e 100644
--- a/interfaces/cython/cantera/mixmaster/ImportFrame.py
+++ b/interfaces/cython/cantera/mixmaster/ImportFrame.py
@@ -1,6 +1,6 @@
 import os, math,sys
 
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
     from tkinter.filedialog import askopenfilename
 else:
diff --git a/interfaces/cython/cantera/mixmaster/KineticsFrame.py b/interfaces/cython/cantera/mixmaster/KineticsFrame.py
index aadbc7a24..d6f7fe56f 100644
--- a/interfaces/cython/cantera/mixmaster/KineticsFrame.py
+++ b/interfaces/cython/cantera/mixmaster/KineticsFrame.py
@@ -2,7 +2,7 @@ from __future__ import print_function
 
 import os, math, sys
 
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/MechManager.py b/interfaces/cython/cantera/mixmaster/MechManager.py
index cf16632a4..a1d2e6e91 100644
--- a/interfaces/cython/cantera/mixmaster/MechManager.py
+++ b/interfaces/cython/cantera/mixmaster/MechManager.py
@@ -1,7 +1,7 @@
 from cantera import *
 
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/NewFlowFrame.py b/interfaces/cython/cantera/mixmaster/NewFlowFrame.py
index 33099bd2c..42a816d40 100644
--- a/interfaces/cython/cantera/mixmaster/NewFlowFrame.py
+++ b/interfaces/cython/cantera/mixmaster/NewFlowFrame.py
@@ -1,7 +1,7 @@
 from cantera import *
 
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/SpeciesFrame.py b/interfaces/cython/cantera/mixmaster/SpeciesFrame.py
index dcae00e0b..b9fb51c63 100644
--- a/interfaces/cython/cantera/mixmaster/SpeciesFrame.py
+++ b/interfaces/cython/cantera/mixmaster/SpeciesFrame.py
@@ -4,7 +4,7 @@
 #
 
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/SpeciesInfo.py b/interfaces/cython/cantera/mixmaster/SpeciesInfo.py
index 1f0b850f6..4d63735dd 100644
--- a/interfaces/cython/cantera/mixmaster/SpeciesInfo.py
+++ b/interfaces/cython/cantera/mixmaster/SpeciesInfo.py
@@ -1,5 +1,5 @@
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/ThermoFrame.py b/interfaces/cython/cantera/mixmaster/ThermoFrame.py
index 6b5f9c96a..8cec3719c 100644
--- a/interfaces/cython/cantera/mixmaster/ThermoFrame.py
+++ b/interfaces/cython/cantera/mixmaster/ThermoFrame.py
@@ -3,7 +3,7 @@
 from cantera import *
 
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/ThermoProp.py b/interfaces/cython/cantera/mixmaster/ThermoProp.py
index b37d1922f..9e0b5ca74 100644
--- a/interfaces/cython/cantera/mixmaster/ThermoProp.py
+++ b/interfaces/cython/cantera/mixmaster/ThermoProp.py
@@ -1,5 +1,5 @@
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/TransportFrame.py b/interfaces/cython/cantera/mixmaster/TransportFrame.py
index 38a8c8212..871c98595 100644
--- a/interfaces/cython/cantera/mixmaster/TransportFrame.py
+++ b/interfaces/cython/cantera/mixmaster/TransportFrame.py
@@ -1,5 +1,5 @@
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/UnitChooser.py b/interfaces/cython/cantera/mixmaster/UnitChooser.py
index 602007b96..16b0e2e45 100644
--- a/interfaces/cython/cantera/mixmaster/UnitChooser.py
+++ b/interfaces/cython/cantera/mixmaster/UnitChooser.py
@@ -1,5 +1,5 @@
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/flowpanel.py b/interfaces/cython/cantera/mixmaster/flowpanel.py
index dde60c79e..585343a28 100644
--- a/interfaces/cython/cantera/mixmaster/flowpanel.py
+++ b/interfaces/cython/cantera/mixmaster/flowpanel.py
@@ -2,7 +2,7 @@
 
 # functionality imports
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/main.py b/interfaces/cython/cantera/mixmaster/main.py
index 7aa4f5144..16e400c45 100644
--- a/interfaces/cython/cantera/mixmaster/main.py
+++ b/interfaces/cython/cantera/mixmaster/main.py
@@ -11,7 +11,7 @@ _app_version = '1.0'
 
 # functionality imports
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
     from tkinter import messagebox
     from tkinter.filedialog import askopenfilename
diff --git a/interfaces/cython/cantera/mixmaster/menu.py b/interfaces/cython/cantera/mixmaster/menu.py
index 904f93f87..33050155c 100644
--- a/interfaces/cython/cantera/mixmaster/menu.py
+++ b/interfaces/cython/cantera/mixmaster/menu.py
@@ -1,5 +1,5 @@
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
 else:
     from Tkinter import *
diff --git a/interfaces/cython/cantera/mixmaster/newflow.py b/interfaces/cython/cantera/mixmaster/newflow.py
index 754999f33..e56021eb1 100644
--- a/interfaces/cython/cantera/mixmaster/newflow.py
+++ b/interfaces/cython/cantera/mixmaster/newflow.py
@@ -1,6 +1,6 @@
 
 import sys
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     from tkinter import *
     from tkinter.filedialog import askopenfilename
     from tkinter import messagebox
diff --git a/interfaces/cython/cantera/mixmaster/utilities.py b/interfaces/cython/cantera/mixmaster/utilities.py
index e2a07fcc3..c1d9951c0 100644
--- a/interfaces/cython/cantera/mixmaster/utilities.py
+++ b/interfaces/cython/cantera/mixmaster/utilities.py
@@ -3,7 +3,7 @@ import os, sys
 import types, traceback
 
 try:
-    if sys.version_info.major == 3:
+    if sys.version_info[0] == 3:
         from tkinter import Tk
         from tkinter import messagebox
     else:
diff --git a/test/python/runCythonTests.py b/test/python/runCythonTests.py
index b342a16eb..cab73baf4 100644
--- a/test/python/runCythonTests.py
+++ b/test/python/runCythonTests.py
@@ -10,7 +10,7 @@ import sys
 import os
 
 cantera_root = os.getcwd().split(os.sep)[:-2]
-if sys.version_info.major == 3:
+if sys.version_info[0] == 3:
     sys.path.insert(0, os.sep.join(cantera_root + ['build', 'python3']))
 else:
     sys.path.insert(0, os.sep.join(cantera_root + ['build', 'python2']))