# DP: distutils: Add an option --install-layout=deb, which
# DP: - installs into $prefix/dist-packages instead of $prefix/site-packages.
# DP: - doesn't encode the python version into the egg name.

--- a/3.9/Lib/distutils/command/install_egg_info.py
+++ b/3.9/Lib/distutils/command/install_egg_info.py
@@ -14,18 +14,38 @@ class install_egg_info(Command):
     description = "Install package's PKG-INFO metadata as an .egg-info file"
     user_options = [
         ('install-dir=', 'd', "directory to install to"),
+        ('install-layout', None, "custom installation layout"),
     ]
 
     def initialize_options(self):
         self.install_dir = None
+        self.install_layout = None
+        self.prefix_option = None
 
     def finalize_options(self):
         self.set_undefined_options('install_lib',('install_dir','install_dir'))
-        basename = "%s-%s-py%d.%d.egg-info" % (
-            to_filename(safe_name(self.distribution.get_name())),
-            to_filename(safe_version(self.distribution.get_version())),
-            *sys.version_info[:2]
-        )
+        self.set_undefined_options('install',('install_layout','install_layout'))
+        self.set_undefined_options('install',('prefix_option','prefix_option'))
+        if self.install_layout:
+            if not self.install_layout.lower() in ['deb', 'unix']:
+                raise DistutilsOptionError(
+                    "unknown value for --install-layout")
+            no_pyver = (self.install_layout.lower() == 'deb')
+        elif self.prefix_option:
+            no_pyver = False
+        else:
+            no_pyver = True
+        if no_pyver:
+            basename = "%s-%s.egg-info" % (
+                to_filename(safe_name(self.distribution.get_name())),
+                to_filename(safe_version(self.distribution.get_version()))
+                )
+        else:
+            basename = "%s-%s-py%d.%d.egg-info" % (
+                to_filename(safe_name(self.distribution.get_name())),
+                to_filename(safe_version(self.distribution.get_version())),
+                *sys.version_info[:2]
+            )
         self.target = os.path.join(self.install_dir, basename)
         self.outputs = [self.target]
 
--- a/3.9/Lib/distutils/command/install.py
+++ b/3.9/Lib/distutils/command/install.py
@@ -35,6 +35,20 @@ INSTALL_SCHEMES = {
         'scripts': '$base/bin',
         'data'   : '$base',
         },
+    'unix_local': {
+        'purelib': '$base/local/lib/python$py_version_short/dist-packages',
+        'platlib': '$platbase/local/lib/python$py_version_short/dist-packages',
+        'headers': '$base/local/include/python$py_version_short/$dist_name',
+        'scripts': '$base/local/bin',
+        'data'   : '$base/local',
+        },
+    'deb_system': {
+        'purelib': '$base/lib/python3/dist-packages',
+        'platlib': '$platbase/lib/python3/dist-packages',
+        'headers': '$base/include/python$py_version_short/$dist_name',
+        'scripts': '$base/bin',
+        'data'   : '$base',
+        },
     'unix_home': {
         'purelib': '$base/lib/python',
         'platlib': '$base/$platlibdir/python',
@@ -131,6 +145,9 @@ class install(Command):
 
         ('record=', None,
          "filename in which to record list of installed files"),
+
+        ('install-layout=', None,
+         "installation layout to choose (known values: deb, unix)"),
         ]
 
     boolean_options = ['compile', 'force', 'skip-build']
@@ -151,6 +168,7 @@ class install(Command):
         self.exec_prefix = None
         self.home = None
         self.user = 0
+        self.prefix_option = None
 
         # These select only the installation base; it's up to the user to
         # specify the installation scheme (currently, that means supplying
@@ -172,6 +190,9 @@ class install(Command):
         self.install_userbase = USER_BASE
         self.install_usersite = USER_SITE
 
+        # enable custom installation, known values: deb
+        self.install_layout = None
+        
         self.compile = None
         self.optimize = None
 
@@ -414,6 +435,7 @@ class install(Command):
             self.install_base = self.install_platbase = self.home
             self.select_scheme("unix_home")
         else:
+            self.prefix_option = self.prefix
             if self.prefix is None:
                 if self.exec_prefix is not None:
                     raise DistutilsOptionError(
@@ -428,7 +450,26 @@ class install(Command):
 
             self.install_base = self.prefix
             self.install_platbase = self.exec_prefix
-            self.select_scheme("unix_prefix")
+            if self.install_layout:
+                if self.install_layout.lower() in ['deb']:
+                    self.select_scheme("deb_system")
+                elif self.install_layout.lower() in ['unix']:
+                    self.select_scheme("unix_prefix")
+                else:
+                    raise DistutilsOptionError(
+                        "unknown value for --install-layout")
+            elif ((self.prefix_option and
+                   os.path.normpath(self.prefix) != '/usr/local')
+                  or sys.base_prefix != sys.prefix
+                  or 'PYTHONUSERBASE' in os.environ
+                  or 'VIRTUAL_ENV' in os.environ
+                  or 'real_prefix' in sys.__dict__):
+                self.select_scheme("unix_prefix")
+            else:
+                if os.path.normpath(self.prefix) == '/usr/local':
+                    self.prefix = self.exec_prefix = '/usr'
+                    self.install_base = self.install_platbase = '/usr'
+                self.select_scheme("unix_local")
 
     def finalize_other(self):
         """Finalizes options for non-posix platforms"""
--- a/3.9/Lib/distutils/sysconfig.py
+++ b/3.9/Lib/distutils/sysconfig.py
@@ -138,6 +138,7 @@ def get_python_lib(plat_specific=0, stan
     If 'prefix' is supplied, use it instead of sys.base_prefix or
     sys.base_exec_prefix -- i.e., ignore 'plat_specific'.
     """
+    is_default_prefix = not prefix or os.path.normpath(prefix) in ('/usr', '/usr/local')
     if prefix is None:
         if standard_lib:
             prefix = plat_specific and BASE_EXEC_PREFIX or BASE_PREFIX
@@ -156,6 +157,12 @@ def get_python_lib(plat_specific=0, stan
                                  "python" + get_python_version())
         if standard_lib:
             return libpython
+        elif (is_default_prefix and
+              'PYTHONUSERBASE' not in os.environ and
+              'VIRTUAL_ENV' not in os.environ and
+              'real_prefix' not in sys.__dict__ and
+              sys.prefix == sys.base_prefix):
+            return os.path.join(prefix, "lib", "python3", "dist-packages")
         else:
             return os.path.join(libpython, "site-packages")
     elif os.name == "nt":
--- a/3.9/Lib/distutils/tests/test_bdist_dumb.py
+++ b/3.9/Lib/distutils/tests/test_bdist_dumb.py
@@ -85,7 +85,7 @@ class BuildDumbTestCase(support.TempdirM
             fp.close()
 
         contents = sorted(filter(None, map(os.path.basename, contents)))
-        wanted = ['foo-0.1-py%s.%s.egg-info' % sys.version_info[:2], 'foo.py']
+        wanted = ['foo-0.1.egg-info', 'foo.py']
         if not sys.dont_write_bytecode:
             wanted.append('foo.%s.pyc' % sys.implementation.cache_tag)
         self.assertEqual(contents, sorted(wanted))
--- a/3.9/Lib/distutils/tests/test_install.py
+++ b/3.9/Lib/distutils/tests/test_install.py
@@ -194,7 +194,7 @@ class InstallTestCase(support.TempdirMan
         found = [os.path.basename(line) for line in content.splitlines()]
         expected = ['hello.py', 'hello.%s.pyc' % sys.implementation.cache_tag,
                     'sayhi',
-                    'UNKNOWN-0.0.0-py%s.%s.egg-info' % sys.version_info[:2]]
+                    'UNKNOWN-0.0.0.egg-info']
         self.assertEqual(found, expected)
 
     def test_record_extensions(self):
@@ -227,7 +227,7 @@ class InstallTestCase(support.TempdirMan
 
         found = [os.path.basename(line) for line in content.splitlines()]
         expected = [_make_ext_name('xx'),
-                    'UNKNOWN-0.0.0-py%s.%s.egg-info' % sys.version_info[:2]]
+                    'UNKNOWN-0.0.0.egg-info']
         self.assertEqual(found, expected)
 
     def test_debug_mode(self):