diff --git a/doc/example-keywords.txt b/doc/example-keywords.txt
index 22a82c264..8cc74559f 100644
--- a/doc/example-keywords.txt
+++ b/doc/example-keywords.txt
@@ -41,5 +41,6 @@ thermodynamic cycle
 thermodynamics
 transport
 tutorial
+units
 user-defined model
 well-stirred reactor
diff --git a/interfaces/cython/SConscript b/interfaces/cython/SConscript
index a5df1e54f..74f83d01e 100644
--- a/interfaces/cython/SConscript
+++ b/interfaces/cython/SConscript
@@ -106,7 +106,7 @@ else:
     localenv.Depends(ext, localenv['cantera_shlib'])
 
 for f in (multi_glob(localenv, 'cantera', 'py') +
-          multi_glob(localenv, 'cantera/*', 'py')):
+          multi_glob(localenv, 'cantera/*', 'py', 'in')):
     localenv.Depends(mod, f)
 
 UNITS = {
diff --git a/samples/python/thermo/isentropic_units.py b/samples/python/thermo/isentropic_units.py
index 20c5d71d8..2220dea1e 100644
--- a/samples/python/thermo/isentropic_units.py
+++ b/samples/python/thermo/isentropic_units.py
@@ -1,10 +1,11 @@
 """
 Isentropic, adiabatic flow example - calculate area ratio vs. Mach number curve
 
-Requires: cantera >= 2.6.0
+Requires: cantera >= 3.0.0
+Keywords: thermodynamics, compressible flow, units
 """
 
-import cantera.units as ct
+import cantera.with_units as ct
 import numpy as np
 ct.units.default_format = ".2F~P"
 label_string = "area ratio\tMach number\ttemperature\tpressure ratio"
diff --git a/samples/python/thermo/rankine_units.py b/samples/python/thermo/rankine_units.py
index 32967eb01..a4e3855bf 100644
--- a/samples/python/thermo/rankine_units.py
+++ b/samples/python/thermo/rankine_units.py
@@ -1,15 +1,17 @@
 """
-A Rankine vapor power cycle
+Calculate the efficiency of a Rankine vapor power cycle using a pure fluid model
+for water. Includes the units of quantities in the calculations.
 
 Requires: Cantera >= 2.6.0
+Keywords: thermodynamics, thermodynamic cycle, non-ideal fluid, units
 """
 
-import cantera.units as ct
+import cantera.with_units as ct
 
 # parameters
-eta_pump = 0.6 * ct.units.dimensionless     # pump isentropic efficiency
+eta_pump = 0.6 * ct.units.dimensionless  # pump isentropic efficiency
 eta_turbine = 0.8 * ct.units.dimensionless # turbine isentropic efficiency
-p_max = 116.03 * ct.units.psi       # maximum pressure
+p_max = 116.03 * ct.units.psi  # maximum pressure
 
 
 def pump(fluid, p_final, eta):
@@ -40,7 +42,7 @@ def expand(fluid, p_final, eta):
     return actual_work
 
 
-def printState(n, fluid):
+def print_state(n, fluid):
     print('\n***************** State {0} ******************'.format(n))
     print(fluid.report())
 
@@ -53,23 +55,23 @@ if __name__ == '__main__':
     w.TQ = 540 * ct.units.degR, 0.0 * ct.units.dimensionless
     h1 = w.h
     p1 = w.P
-    printState(1, w)
+    print_state(1, w)
 
     # pump it adiabatically to p_max
     pump_work = pump(w, p_max, eta_pump)
     h2 = w.h
-    printState(2, w)
+    print_state(2, w)
 
     # heat it at constant pressure until it reaches the saturated vapor state
     # at this pressure
     w.PQ = p_max, 1.0 * ct.units.dimensionless
     h3 = w.h
     heat_added = h3 - h2
-    printState(3, w)
+    print_state(3, w)
 
     # expand back to p1
     turbine_work = expand(w, p1, eta_turbine)
-    printState(4, w)
+    print_state(4, w)
 
     # efficiency
     eff = (turbine_work - pump_work)/heat_added
diff --git a/samples/python/thermo/sound_speed_units.py b/samples/python/thermo/sound_speed_units.py
index fe7c4f2a2..c0abca7ab 100644
--- a/samples/python/thermo/sound_speed_units.py
+++ b/samples/python/thermo/sound_speed_units.py
@@ -2,14 +2,15 @@
 Compute the "equilibrium" and "frozen" sound speeds for a gas
 
 Requires: cantera >= 2.6.0
+Keywords: thermodynamics, equilibrium
 """
 
-import cantera.units as ct
+import cantera.with_units as ct
 import numpy as np
 
 ct.units.default_format = ".2F~P"
 
-def equilSoundSpeeds(gas, rtol=1.0e-6, max_iter=5000):
+def equilibrium_sound_speeds(gas, rtol=1.0e-6, max_iter=5000):
     """
     Returns a tuple containing the equilibrium and frozen sound speeds for a
     gas with an equilibrium composition.  The gas is first set to an
@@ -43,6 +44,7 @@ def equilSoundSpeeds(gas, rtol=1.0e-6, max_iter=5000):
 
     # compute the frozen sound speed using the ideal gas expression as a check
     gamma = gas.cp/gas.cv
+    gamma * ct.units.molar_gas_constant
     afrozen2 = np.sqrt(gamma * ct.units.molar_gas_constant * gas.T /
                          gas.mean_molecular_weight).to("ft/s")
 
@@ -56,4 +58,4 @@ if __name__ == "__main__":
     print("Temperature      Equilibrium Sound Speed     Frozen Sound Speed      Frozen Sound Speed Check")
     for T in T_range:
         gas.TP = T, 1.0 * ct.units.atm
-        print(T, *equilSoundSpeeds(gas), sep = "               ")
+        print(T, *equilibrium_sound_speeds(gas), sep = "               ")