SCons now builds the Cython-based Python 3 package

SConstruct

@@ -287,6 +287,30 @@ opts.AddVariables(
            default on Windows), then the Package will be installed to the system
            default 'site-packages' directory.""",
         defaults.python_prefix, PathVariable.PathAccept),
+    EnumVariable(
+        'python3_package',
+        """Controls whether or not the Python 3 module will be built. By
+            default, the module will be built if the Python 3 interpreter can
+            be found""",
+        'default', ('y','n','default')),
+    PathVariable(
+        'python3_cmd',
+        """ The name (full path if necessary) of the Python 3 interpreter.
+        Required to build the Python 3 module.""",
+        'python3', PathVariable.PathAccept),
+    PathVariable(
+        'python3_array_home',
+        """"If numpy was installed to a custom location (e.g. using the --home
+            option, set this to the directory for numpy""",
+        '', PathVariable.PathAccept),
+    PathVariable(
+        'python3_prefix',
+        """Use this option if you want to install the Cantera Python 3 package to
+           an alternate location. On Unix-like systems, the default is the same
+           as the $prefix option. If this option is set to the empty string (the
+           default on Windows), then the Package will be installed to the system
+           default 'site-packages' directory.""",
+        defaults.python_prefix, PathVariable.PathAccept),
     EnumVariable(
         'matlab_toolbox',
         """This variable controls whether the Matlab toolbox will be built. If
@@ -739,6 +763,8 @@ int main(int argc, char** argv) {
 
 env = conf.Finish()
 
+
+# Python 2 Package Settings
 if env['python_package'] in ('full','default'):
     # Test to see if we can import the specified array module
     warnNoPython = False
@@ -769,6 +795,27 @@ else:
     env['python_array_include'] = ''
 
 
+# Python 3 Package Settings
+if env['python3_package'] in ('y', 'default'):
+    # See if we can execute the Python 3 interpreter
+    try:
+        ret = subprocess.check_call([env['python3_cmd'],'-c','""'])
+    except OSError:
+        ret = -1
+
+    if ret:
+        if env['python3_package'] == 'default':
+            print ('INFO: Not building the Python 3 package because the Python '
+                   '3 interpreter %r could not be found' % env['python3_cmd'])
+            env['python3_package'] = 'n'
+        else:
+            print ('ERROR: Could not execute the Python 3 interpreter %r' %
+                   env['python3_cmd'])
+            sys.exit(1)
+    else:
+        env['python3_package'] = 'y'
+
+
 # Matlab Toolbox settings
 if env['matlab_path'] != '' and env['matlab_toolbox'] == 'default':
     env['matlab_toolbox'] = 'y'
@@ -1154,6 +1201,10 @@ if env['python_package'] in ('full','minimal'):
     VariantDir('build/src/python', 'src/python', duplicate=0)
     SConscript('build/src/python/SConscript')
 
+if env['python3_package'] == 'y':
+    VariantDir('build/python3', 'interfaces/cython', duplicate=0)
+    SConscript('build/cython/SConscript')
+
 SConscript('build/src/apps/SConscript')
 
 if env['OS'] != 'Windows':

interfaces/cython/SConscript

@@ -0,0 +1,49 @@
+""" Cython-based Python Module for Python 3 """
+from buildutils import *
+
+Import('env', 'build', 'install')
+
+localenv = env.Clone()
+
+libDirs = ('../../build/lib', localenv['sundials_libdir'],
+           localenv['boost_lib_dir'])
+localenv['py_cantera_libs'] = repr(localenv['cantera_libs'])
+localenv['py_libdirs'] = repr([x for x in libDirs if x])
+
+if localenv['CC'] == 'cl':
+    localenv['py_extra_compiler_args'] = repr(['/EHsc'])
+else:
+    localenv['py_extra_compiler_args'] = repr([])
+
+dataFiles = localenv.RecursiveInstall('#interfaces/cython/cantera/data',
+                                      '#data/inputs', ['\\.inp$', '\\.in$'])
+build(dataFiles)
+
+if localenv['python3_package'] == 'y':
+    info = getCommandOutput(localenv['python3_cmd'], '-c',
+                            '\n'.join(("from distutils.sysconfig import *",
+                                       "import numpy",
+                                       "print(get_config_var('SO'))",
+                                       "print(numpy.get_include())")))
+
+    module_extension, localenv['python3_array_include'] = info.split('\n')
+
+    incDirs = (".", "../../include", localenv['python3_array_include'],
+               localenv['sundials_include'], localenv['boost_inc_dir'])
+    localenv['py_include_dirs'] = repr([x for x in incDirs if x])
+
+
+    make_setup = localenv.SubstFile('#interfaces/cython/setup.py',
+                                    '#interfaces/cython/setup.py.in')
+    build(make_setup)
+
+    opts = '--build-lib=../../build/python3 --build-temp=../../build/temp'
+    mod = build(localenv.Command('cantera/_cantera%s' % module_extension,
+                                 'setup.py',
+                                 'cd interfaces/cython && '
+                                 '$python3_cmd $SOURCE.name build %s' % opts))
+
+    localenv.AddPreAction(mod, Delete('interfaces/cython/cantera/_cantera.cpp'))
+
+    for f in mglob(localenv, 'cantera', 'pyx', 'pxd'):
+        localenv.Depends(mod, f)

site_scons/buildutils.py

@@ -545,3 +545,18 @@ def getSpawn(env):
         return rv
 
     return ourSpawn
+
+def getCommandOutput(cmd, *args):
+    """
+    Run a command with arguments and return its output.
+    Substitute for subprocess.check_output which is only available
+    in Python >= 2.7
+    """
+    proc = subprocess.Popen([cmd] + list(args),
+                            stdout=subprocess.PIPE,
+                            stderr=subprocess.PIPE)
+    data, err = proc.communicate()
+    if proc.returncode:
+        raise OSError(err)
+
+    return data.strip()

src/python/SConscript

@@ -105,30 +105,3 @@ elif localenv['PYTHON_INSTALLER'] == 'binary':
 if localenv['python_package'] == 'full':
     install(localenv.RecursiveInstall, pjoin('$inst_sampledir', 'python'),
             '#samples/python')
-
-#################################
-### New Python Module: Cython ###
-#################################
-
-localenv = env.Clone()
-incDirs = (".", "../../include", localenv['python_array_include'],
-           localenv['sundials_include'], localenv['boost_inc_dir'])
-libDirs = ('../../build/lib', localenv['sundials_libdir'],
-           localenv['boost_lib_dir'])
-
-localenv['py_include_dirs'] = repr([x for x in incDirs if x])
-localenv['py_cantera_libs'] = repr(localenv['cantera_libs'])
-localenv['py_libdirs'] = repr([x for x in libDirs if x])
-
-if localenv['CC'] == 'cl':
-    localenv['py_extra_compiler_args'] = repr(['/EHsc'])
-else:
-    localenv['py_extra_compiler_args'] = repr([])
-
-dataFiles = localenv.RecursiveInstall('#interfaces/cython/cantera/data',
-                                      '#data/inputs', ['\\.inp$', '\\.in$'])
-build(dataFiles)
-
-make_setup = localenv.SubstFile('#interfaces/cython/setup.py',
-                                '#interfaces/cython/setup.py.in')
-build(make_setup)