# DP: Add schemes 'deb_system' and 'posix_local', make the latter the default

Index: b/Lib/sysconfig.py
===================================================================
--- a/Lib/sysconfig.py
+++ b/Lib/sysconfig.py
@@ -31,6 +31,30 @@ _INSTALL_SCHEMES = {
         'scripts': '{base}/bin',
         'data': '{base}',
         },
+    'deb_system': {
+        'stdlib': '{installed_base}/lib/python{py_version_short}',
+        'platstdlib': '{platbase}/lib/python{py_version_short}',
+        'purelib': '{base}/lib/python3/dist-packages',
+        'platlib': '{platbase}/lib/python3/dist-packages',
+        'include':
+            '{installed_base}/include/python{py_version_short}{abiflags}',
+        'platinclude':
+            '{installed_platbase}/include/python{py_version_short}{abiflags}',
+        'scripts': '{base}/bin',
+        'data': '{base}',
+        },
+    'posix_local': {
+        'stdlib': '{installed_base}/lib/python{py_version_short}',
+        'platstdlib': '{platbase}/lib/python{py_version_short}',
+        'purelib': '{base}/local/lib/python{py_version_short}/dist-packages',
+        'platlib': '{platbase}/local/lib/python{py_version_short}/dist-packages',
+        'include':
+            '{installed_base}/local/include/python{py_version_short}{abiflags}',
+        'platinclude':
+            '{installed_platbase}/local/include/python{py_version_short}{abiflags}',
+        'scripts': '{base}/local/bin',
+        'data': '{base}',
+        },
     'posix_home': {
         'stdlib': '{installed_base}/lib/python',
         'platstdlib': '{base}/lib/python',
@@ -136,7 +160,7 @@ def is_python_build(check_home=False):
 _PYTHON_BUILD = is_python_build(True)
 
 if _PYTHON_BUILD:
-    for scheme in ('posix_prefix', 'posix_home'):
+    for scheme in ('posix_prefix', 'posix_home', 'posix_local', 'deb_system'):
         _INSTALL_SCHEMES[scheme]['include'] = '{srcdir}/Include'
         _INSTALL_SCHEMES[scheme]['platinclude'] = '{projectbase}/.'
 
@@ -174,7 +198,16 @@ def _expand_vars(scheme, vars):
 def _get_default_scheme():
     if os.name == 'posix':
         # the default scheme for posix is posix_prefix
-        return 'posix_prefix'
+        if 'real_prefix' in sys.__dict__ or 'VIRTUAL_ENV' in os.environ:
+            # virtual environments
+            return 'posix_prefix'
+        else:
+            # default to /usr for package builds, /usr/local otherwise
+            deb_build = os.environ.get('DEB_PYTHON_INSTALL_LAYOUT', 'posix_local')
+            if deb_build in ('deb', 'deb_system'):
+                return 'deb_system'
+            else:
+                return 'posix_local'
     return os.name
 
 
@@ -472,7 +505,7 @@ def get_config_h_filename():
         else:
             inc_dir = _sys_home or _PROJECT_BASE
     else:
-        inc_dir = get_path('platinclude')
+        inc_dir = get_path('platinclude', 'posix_prefix')
     return os.path.join(inc_dir, 'pyconfig.h')
 
 
Index: b/Lib/test/test_sysconfig.py
===================================================================
--- a/Lib/test/test_sysconfig.py
+++ b/Lib/test/test_sysconfig.py
@@ -227,8 +227,8 @@ class TestSysConfig(unittest.TestCase):
         self.assertTrue(os.path.isfile(config_h), config_h)
 
     def test_get_scheme_names(self):
-        wanted = ('nt', 'nt_user', 'osx_framework_user',
-                  'posix_home', 'posix_prefix', 'posix_user')
+        wanted = ('deb_system', 'nt', 'nt_user', 'osx_framework_user',
+                  'posix_home', 'posix_local', 'posix_prefix', 'posix_user')
         self.assertEqual(get_scheme_names(), wanted)
 
     @skip_unless_symlink