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move _PackageBoundObject into Scaffold

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This commit is contained in:
David Lord 2021-03-08 12:16:39 -08:00
parent 3316604822
commit 9f7c602a84
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3 changed files with 343 additions and 352 deletions
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5
src/flask/app.py
View file

@ -29,7 +29,6 @@ from .globals import _request_ctx_stack
from .globals import g from .globals import g
from .globals import request from .globals import request
from .globals import session from .globals import session
from .helpers import find_package
from .helpers import get_debug_flag from .helpers import get_debug_flag
from .helpers import get_env from .helpers import get_env
from .helpers import get_flashed_messages from .helpers import get_flashed_messages
@ -40,6 +39,7 @@ from .json import jsonify
from .logging import create_logger from .logging import create_logger
from .scaffold import _endpoint_from_view_func from .scaffold import _endpoint_from_view_func
from .scaffold import _sentinel from .scaffold import _sentinel
from .scaffold import find_package
from .scaffold import Scaffold from .scaffold import Scaffold
from .scaffold import setupmethod from .scaffold import setupmethod
from .sessions import SecureCookieSessionInterface from .sessions import SecureCookieSessionInterface
@ -2026,6 +2026,3 @@ class Flask(Scaffold):
WSGI application. This calls :meth:`wsgi_app` which can be WSGI application. This calls :meth:`wsgi_app` which can be
wrapped to applying middleware.""" wrapped to applying middleware."""
return self.wsgi_app(environ, start_response) return self.wsgi_app(environ, start_response)
def __repr__(self):
return f"<{type(self).__name__} {self.name!r}>"

303
src/flask/helpers.py
View file

@ -1,13 +1,10 @@
import os import os
import pkgutil
import socket import socket
import sys
import warnings import warnings
from functools import update_wrapper from functools import update_wrapper
from threading import RLock from threading import RLock
import werkzeug.utils import werkzeug.utils
from jinja2 import FileSystemLoader
from werkzeug.exceptions import NotFound from werkzeug.exceptions import NotFound
from werkzeug.routing import BuildError from werkzeug.routing import BuildError
from werkzeug.urls import url_quote from werkzeug.urls import url_quote
@ -677,157 +674,6 @@ def send_from_directory(directory, path, **kwargs):
) )
def get_root_path(import_name):
"""Returns the path to a package or cwd if that cannot be found. This
returns the path of a package or the folder that contains a module.
Not to be confused with the package path returned by :func:`find_package`.
"""
# Module already imported and has a file attribute. Use that first.
mod = sys.modules.get(import_name)
if mod is not None and hasattr(mod, "__file__"):
return os.path.dirname(os.path.abspath(mod.__file__))
# Next attempt: check the loader.
loader = pkgutil.get_loader(import_name)
# Loader does not exist or we're referring to an unloaded main module
# or a main module without path (interactive sessions), go with the
# current working directory.
if loader is None or import_name == "__main__":
return os.getcwd()
if hasattr(loader, "get_filename"):
filepath = loader.get_filename(import_name)
else:
# Fall back to imports.
__import__(import_name)
mod = sys.modules[import_name]
filepath = getattr(mod, "__file__", None)
# If we don't have a filepath it might be because we are a
# namespace package. In this case we pick the root path from the
# first module that is contained in our package.
if filepath is None:
raise RuntimeError(
"No root path can be found for the provided module"
f" {import_name!r}. This can happen because the module"
" came from an import hook that does not provide file"
" name information or because it's a namespace package."
" In this case the root path needs to be explicitly"
" provided."
)
# filepath is import_name.py for a module, or __init__.py for a package.
return os.path.dirname(os.path.abspath(filepath))
def _matching_loader_thinks_module_is_package(loader, mod_name):
"""Given the loader that loaded a module and the module this function
attempts to figure out if the given module is actually a package.
"""
cls = type(loader)
# If the loader can tell us if something is a package, we can
# directly ask the loader.
if hasattr(loader, "is_package"):
return loader.is_package(mod_name)
# importlib's namespace loaders do not have this functionality but
# all the modules it loads are packages, so we can take advantage of
# this information.
elif cls.__module__ == "_frozen_importlib" and cls.__name__ == "NamespaceLoader":
return True
# Otherwise we need to fail with an error that explains what went
# wrong.
raise AttributeError(
f"{cls.__name__}.is_package() method is missing but is required"
" for PEP 302 import hooks."
)
def _find_package_path(root_mod_name):
"""Find the path where the module's root exists in"""
import importlib.util
try:
spec = importlib.util.find_spec(root_mod_name)
if spec is None:
raise ValueError("not found")
# ImportError: the machinery told us it does not exist
# ValueError:
# - the module name was invalid
# - the module name is __main__
# - *we* raised `ValueError` due to `spec` being `None`
except (ImportError, ValueError):
pass # handled below
else:
# namespace package
if spec.origin in {"namespace", None}:
return os.path.dirname(next(iter(spec.submodule_search_locations)))
# a package (with __init__.py)
elif spec.submodule_search_locations:
return os.path.dirname(os.path.dirname(spec.origin))
# just a normal module
else:
return os.path.dirname(spec.origin)
# we were unable to find the `package_path` using PEP 451 loaders
loader = pkgutil.get_loader(root_mod_name)
if loader is None or root_mod_name == "__main__":
# import name is not found, or interactive/main module
return os.getcwd()
else:
if hasattr(loader, "get_filename"):
filename = loader.get_filename(root_mod_name)
elif hasattr(loader, "archive"):
# zipimporter's loader.archive points to the .egg or .zip
# archive filename is dropped in call to dirname below.
filename = loader.archive
else:
# At least one loader is missing both get_filename and archive:
# Google App Engine's HardenedModulesHook
#
# Fall back to imports.
__import__(root_mod_name)
filename = sys.modules[root_mod_name].__file__
package_path = os.path.abspath(os.path.dirname(filename))
# In case the root module is a package we need to chop of the
# rightmost part. This needs to go through a helper function
# because of namespace packages.
if _matching_loader_thinks_module_is_package(loader, root_mod_name):
package_path = os.path.dirname(package_path)
return package_path
def find_package(import_name):
"""Finds a package and returns the prefix (or None if the package is
not installed) as well as the folder that contains the package or
module as a tuple. The package path returned is the module that would
have to be added to the pythonpath in order to make it possible to
import the module. The prefix is the path below which a UNIX like
folder structure exists (lib, share etc.).
"""
root_mod_name, _, _ = import_name.partition(".")
package_path = _find_package_path(root_mod_name)
site_parent, site_folder = os.path.split(package_path)
py_prefix = os.path.abspath(sys.prefix)
if package_path.startswith(py_prefix):
return py_prefix, package_path
elif site_folder.lower() == "site-packages":
parent, folder = os.path.split(site_parent)
# Windows like installations
if folder.lower() == "lib":
base_dir = parent
# UNIX like installations
elif os.path.basename(parent).lower() == "lib":
base_dir = os.path.dirname(parent)
else:
base_dir = site_parent
return base_dir, package_path
return None, package_path
class locked_cached_property: class locked_cached_property:
"""A decorator that converts a function into a lazy property. The """A decorator that converts a function into a lazy property. The
function wrapped is called the first time to retrieve the result function wrapped is called the first time to retrieve the result
@ -854,155 +700,6 @@ class locked_cached_property:
return value return value
class _PackageBoundObject:
#: The name of the package or module that this app belongs to. Do not
#: change this once it is set by the constructor.
import_name = None
#: Location of the template files to be added to the template lookup.
#: ``None`` if templates should not be added.
template_folder = None
#: Absolute path to the package on the filesystem. Used to look up
#: resources contained in the package.
root_path = None
def __init__(self, import_name, template_folder=None, root_path=None):
self.import_name = import_name
self.template_folder = template_folder
if root_path is None:
root_path = get_root_path(self.import_name)
self.root_path = root_path
self._static_folder = None
self._static_url_path = None
# circular import
from .cli import AppGroup
#: The Click command group for registration of CLI commands
#: on the application and associated blueprints. These commands
#: are accessible via the :command:`flask` command once the
#: application has been discovered and blueprints registered.
self.cli = AppGroup()
@property
def static_folder(self):
"""The absolute path to the configured static folder."""
if self._static_folder is not None:
return os.path.join(self.root_path, self._static_folder)
@static_folder.setter
def static_folder(self, value):
if value is not None:
value = os.fspath(value).rstrip(r"\/")
self._static_folder = value
@property
def static_url_path(self):
"""The URL prefix that the static route will be accessible from.
If it was not configured during init, it is derived from
:attr:`static_folder`.
"""
if self._static_url_path is not None:
return self._static_url_path
if self.static_folder is not None:
basename = os.path.basename(self.static_folder)
return f"/{basename}".rstrip("/")
@static_url_path.setter
def static_url_path(self, value):
if value is not None:
value = value.rstrip("/")
self._static_url_path = value
@property
def has_static_folder(self):
"""This is ``True`` if the package bound object's container has a
folder for static files.
.. versionadded:: 0.5
"""
return self.static_folder is not None
@locked_cached_property
def jinja_loader(self):
"""The Jinja loader for this package bound object.
.. versionadded:: 0.5
"""
if self.template_folder is not None:
return FileSystemLoader(os.path.join(self.root_path, self.template_folder))
def get_send_file_max_age(self, filename):
"""Used by :func:`send_file` to determine the ``max_age`` cache
value for a given file path if it wasn't passed.
By default, this returns :data:`SEND_FILE_MAX_AGE_DEFAULT` from
the configuration of :data:`~flask.current_app`. This defaults
to ``None``, which tells the browser to use conditional requests
instead of a timed cache, which is usually preferable.
.. versionchanged:: 2.0
The default configuration is ``None`` instead of 12 hours.
.. versionadded:: 0.9
"""
value = current_app.send_file_max_age_default
if value is None:
return None
return total_seconds(value)
def send_static_file(self, filename):
"""Function used internally to send static files from the static
folder to the browser.
.. versionadded:: 0.5
"""
if not self.has_static_folder:
raise RuntimeError("No static folder for this object")
# send_file only knows to call get_send_file_max_age on the app,
# call it here so it works for blueprints too.
max_age = self.get_send_file_max_age(filename)
return send_from_directory(self.static_folder, filename, max_age=max_age)
def open_resource(self, resource, mode="rb"):
"""Opens a resource from the application's resource folder. To see
how this works, consider the following folder structure::
/myapplication.py
/schema.sql
/static
/style.css
/templates
/layout.html
/index.html
If you want to open the :file:`schema.sql` file you would do the
following::
with app.open_resource('schema.sql') as f:
contents = f.read()
do_something_with(contents)
:param resource: the name of the resource. To access resources within
subfolders use forward slashes as separator.
:param mode: Open file in this mode. Only reading is supported,
valid values are "r" (or "rt") and "rb".
"""
if mode not in {"r", "rt", "rb"}:
raise ValueError("Resources can only be opened for reading")
return open(os.path.join(self.root_path, resource), mode)
def total_seconds(td): def total_seconds(td):
"""Returns the total seconds from a timedelta object. """Returns the total seconds from a timedelta object.

387
src/flask/scaffold.py
View file

@ -1,10 +1,17 @@
import os
import pkgutil
import sys
from collections import defaultdict from collections import defaultdict
from functools import update_wrapper from functools import update_wrapper
from jinja2 import FileSystemLoader
from werkzeug.exceptions import default_exceptions from werkzeug.exceptions import default_exceptions
from werkzeug.exceptions import HTTPException from werkzeug.exceptions import HTTPException
from .helpers import _PackageBoundObject from .cli import AppGroup
from .globals import current_app
from .helpers import locked_cached_property
from .helpers import send_from_directory
from .templating import _default_template_ctx_processor from .templating import _default_template_ctx_processor
# a singleton sentinel value for parameter defaults # a singleton sentinel value for parameter defaults
@ -19,21 +26,28 @@ def setupmethod(f):
def wrapper_func(self, *args, **kwargs): def wrapper_func(self, *args, **kwargs):
if self._is_setup_finished(): if self._is_setup_finished():
raise AssertionError( raise AssertionError(
"A setup function was called after the " "A setup function was called after the first request "
"first request was handled. This usually indicates a bug " "was handled. This usually indicates a bug in the"
"in the application where a module was not imported " " application where a module was not imported and"
"and decorators or other functionality was called too late.\n" " decorators or other functionality was called too"
"To fix this make sure to import all your view modules, " " late.\nTo fix this make sure to import all your view"
"database models and everything related at a central place " " modules, database models, and everything related at a"
"before the application starts serving requests." " central place before the application starts serving"
" requests."
) )
return f(self, *args, **kwargs) return f(self, *args, **kwargs)
return update_wrapper(wrapper_func, f) return update_wrapper(wrapper_func, f)
class Scaffold(_PackageBoundObject): class Scaffold:
"""A common base for class Flask and class Blueprint.""" """A common base for :class:`~flask.app.Flask` and
:class:`~flask.blueprints.Blueprint`.
"""
name: str
_static_folder = None
_static_url_path = None
#: Skeleton local JSON decoder class to use. #: Skeleton local JSON decoder class to use.
#: Set to ``None`` to use the app's :class:`~flask.app.Flask.json_encoder`. #: Set to ``None`` to use the app's :class:`~flask.app.Flask.json_encoder`.
@ -43,18 +57,6 @@ class Scaffold(_PackageBoundObject):
#: Set to ``None`` to use the app's :class:`~flask.app.Flask.json_decoder`. #: Set to ``None`` to use the app's :class:`~flask.app.Flask.json_decoder`.
json_decoder = None json_decoder = None
#: The name of the package or module that this app belongs to. Do not
#: change this once it is set by the constructor.
import_name = None
#: Location of the template files to be added to the template lookup.
#: ``None`` if templates should not be added.
template_folder = None
#: Absolute path to the package on the filesystem. Used to look up
#: resources contained in the package.
root_path = None
def __init__( def __init__(
self, self,
import_name, import_name,
@ -63,14 +65,31 @@ class Scaffold(_PackageBoundObject):
template_folder=None, template_folder=None,
root_path=None, root_path=None,
): ):
super().__init__( #: The name of the package or module that this object belongs
import_name=import_name, #: to. Do not change this once it is set by the constructor.
template_folder=template_folder, self.import_name = import_name
root_path=root_path,
)
self.static_folder = static_folder self.static_folder = static_folder
self.static_url_path = static_url_path self.static_url_path = static_url_path
#: The path to the templates folder, relative to
#: :attr:`root_path`, to add to the template loader. ``None`` if
#: templates should not be added.
self.template_folder = template_folder
if root_path is None:
root_path = get_root_path(self.import_name)
#: Absolute path to the package on the filesystem. Used to look
#: up resources contained in the package.
self.root_path = root_path
#: The Click command group for registering CLI commands for this
#: object. The commands are available from the ``flask`` command
#: once the application has been discovered and blueprints have
#: been registered.
self.cli = AppGroup()
#: A dictionary of all view functions registered. The keys will #: A dictionary of all view functions registered. The keys will
#: be function names which are also used to generate URLs and #: be function names which are also used to generate URLs and
#: the values are the function objects themselves. #: the values are the function objects themselves.
@ -146,9 +165,127 @@ class Scaffold(_PackageBoundObject):
#: .. versionadded:: 0.7 #: .. versionadded:: 0.7
self.url_default_functions = defaultdict(list) self.url_default_functions = defaultdict(list)
def __repr__(self):
return f"<{type(self).__name__} {self.name!r}>"
def _is_setup_finished(self): def _is_setup_finished(self):
raise NotImplementedError raise NotImplementedError
@property
def static_folder(self):
"""The absolute path to the configured static folder. ``None``
if no static folder is set.
"""
if self._static_folder is not None:
return os.path.join(self.root_path, self._static_folder)
@static_folder.setter
def static_folder(self, value):
if value is not None:
value = os.fspath(value).rstrip(r"\/")
self._static_folder = value
@property
def has_static_folder(self):
"""``True`` if :attr:`static_folder` is set.
.. versionadded:: 0.5
"""
return self.static_folder is not None
@property
def static_url_path(self):
"""The URL prefix that the static route will be accessible from.
If it was not configured during init, it is derived from
:attr:`static_folder`.
"""
if self._static_url_path is not None:
return self._static_url_path
if self.static_folder is not None:
basename = os.path.basename(self.static_folder)
return f"/{basename}".rstrip("/")
@static_url_path.setter
def static_url_path(self, value):
if value is not None:
value = value.rstrip("/")
self._static_url_path = value
def get_send_file_max_age(self, filename):
"""Used by :func:`send_file` to determine the ``max_age`` cache
value for a given file path if it wasn't passed.
By default, this returns :data:`SEND_FILE_MAX_AGE_DEFAULT` from
the configuration of :data:`~flask.current_app`. This defaults
to ``None``, which tells the browser to use conditional requests
instead of a timed cache, which is usually preferable.
.. versionchanged:: 2.0
The default configuration is ``None`` instead of 12 hours.
.. versionadded:: 0.9
"""
value = current_app.send_file_max_age_default
if value is None:
return None
return int(value.total_seconds())
def send_static_file(self, filename):
"""The view function used to serve files from
:attr:`static_folder`. A route is automatically registered for
this view at :attr:`static_url_path` if :attr:`static_folder` is
set.
.. versionadded:: 0.5
"""
if not self.has_static_folder:
raise RuntimeError("'static_folder' must be set to serve static_files.")
# send_file only knows to call get_send_file_max_age on the app,
# call it here so it works for blueprints too.
max_age = self.get_send_file_max_age(filename)
return send_from_directory(self.static_folder, filename, max_age=max_age)
@locked_cached_property
def jinja_loader(self):
"""The Jinja loader for this object's templates. By default this
is a class :class:`jinja2.loaders.FileSystemLoader` to
:attr:`template_folder` if it is set.
.. versionadded:: 0.5
"""
if self.template_folder is not None:
return FileSystemLoader(os.path.join(self.root_path, self.template_folder))
def open_resource(self, resource, mode="rb"):
"""Open a resource file relative to :attr:`root_path` for
reading.
For example, if the file ``schema.sql`` is next to the file
``app.py`` where the ``Flask`` app is defined, it can be opened
with:
.. code-block:: python
with app.open_resource("schema.sql") as f:
conn.executescript(f.read())
:param resource: Path to the resource relative to
:attr:`root_path`.
:param mode: Open the file in this mode. Only reading is
supported, valid values are "r" (or "rt") and "rb".
"""
if mode not in {"r", "rt", "rb"}:
raise ValueError("Resources can only be opened for reading.")
return open(os.path.join(self.root_path, resource), mode)
def _method_route(self, method, rule, options): def _method_route(self, method, rule, options):
if "methods" in options: if "methods" in options:
raise TypeError("Use the 'route' decorator to use the 'methods' argument.") raise TypeError("Use the 'route' decorator to use the 'methods' argument.")
@ -192,27 +329,19 @@ class Scaffold(_PackageBoundObject):
def route(self, rule, **options): def route(self, rule, **options):
"""A decorator that is used to register a view function for a """A decorator that is used to register a view function for a
given URL rule. This does the same thing as :meth:`add_url_rule` given URL rule. This does the same thing as :meth:`add_url_rule`
but is intended for decorator usage:: but is used as a decorator. See :meth:`add_url_rule` and
:ref:`url-route-registrations` for more information.
@app.route('/') .. code-block:: python
@app.route("/")
def index(): def index():
return 'Hello World' return "Hello World"
For more information refer to :ref:`url-route-registrations`. :param rule: The URL rule as a string.
:param options: The options to be forwarded to the underlying
:param rule: the URL rule as string :class:`~werkzeug.routing.Rule` object.
:param endpoint: the endpoint for the registered URL rule. Flask
itself assumes the name of the view function as
endpoint
:param options: the options to be forwarded to the underlying
:class:`~werkzeug.routing.Rule` object. A change
to Werkzeug is handling of method options. methods
is a list of methods this rule should be limited
to (``GET``, ``POST`` etc.). By default a rule
just listens for ``GET`` (and implicitly ``HEAD``).
Starting with Flask 0.6, ``OPTIONS`` is implicitly
added and handled by the standard request handling.
""" """
def decorator(f): def decorator(f):
@ -451,3 +580,171 @@ def _endpoint_from_view_func(view_func):
""" """
assert view_func is not None, "expected view func if endpoint is not provided." assert view_func is not None, "expected view func if endpoint is not provided."
return view_func.__name__ return view_func.__name__
def get_root_path(import_name):
"""Find the root path of a package, or the path that contains a
module. If it cannot be found, returns the current working
directory.
Not to be confused with the value returned by :func:`find_package`.
:meta private:
"""
# Module already imported and has a file attribute. Use that first.
mod = sys.modules.get(import_name)
if mod is not None and hasattr(mod, "__file__"):
return os.path.dirname(os.path.abspath(mod.__file__))
# Next attempt: check the loader.
loader = pkgutil.get_loader(import_name)
# Loader does not exist or we're referring to an unloaded main
# module or a main module without path (interactive sessions), go
# with the current working directory.
if loader is None or import_name == "__main__":
return os.getcwd()
if hasattr(loader, "get_filename"):
filepath = loader.get_filename(import_name)
else:
# Fall back to imports.
__import__(import_name)
mod = sys.modules[import_name]
filepath = getattr(mod, "__file__", None)
# If we don't have a file path it might be because it is a
# namespace package. In this case pick the root path from the
# first module that is contained in the package.
if filepath is None:
raise RuntimeError(
"No root path can be found for the provided module"
f" {import_name!r}. This can happen because the module"
" came from an import hook that does not provide file"
" name information or because it's a namespace package."
" In this case the root path needs to be explicitly"
" provided."
)
# filepath is import_name.py for a module, or __init__.py for a package.
return os.path.dirname(os.path.abspath(filepath))
def _matching_loader_thinks_module_is_package(loader, mod_name):
"""Attempt to figure out if the given name is a package or a module.
:param: loader: The loader that handled the name.
:param mod_name: The name of the package or module.
"""
# Use loader.is_package if it's available.
if hasattr(loader, "is_package"):
return loader.is_package(mod_name)
cls = type(loader)
# NamespaceLoader doesn't implement is_package, but all names it
# loads must be packages.
if cls.__module__ == "_frozen_importlib" and cls.__name__ == "NamespaceLoader":
return True
# Otherwise we need to fail with an error that explains what went
# wrong.
raise AttributeError(
f"'{cls.__name__}.is_package()' must be implemented for PEP 302"
f" import hooks."
)
def _find_package_path(root_mod_name):
"""Find the path that contains the package or module."""
try:
spec = importlib.util.find_spec(root_mod_name)
if spec is None:
raise ValueError("not found")
# ImportError: the machinery told us it does not exist
# ValueError:
# - the module name was invalid
# - the module name is __main__
# - *we* raised `ValueError` due to `spec` being `None`
except (ImportError, ValueError):
pass # handled below
else:
# namespace package
if spec.origin in {"namespace", None}:
return os.path.dirname(next(iter(spec.submodule_search_locations)))
# a package (with __init__.py)
elif spec.submodule_search_locations:
return os.path.dirname(os.path.dirname(spec.origin))
# just a normal module
else:
return os.path.dirname(spec.origin)
# we were unable to find the `package_path` using PEP 451 loaders
loader = pkgutil.get_loader(root_mod_name)
if loader is None or root_mod_name == "__main__":
# import name is not found, or interactive/main module
return os.getcwd()
if hasattr(loader, "get_filename"):
filename = loader.get_filename(root_mod_name)
elif hasattr(loader, "archive"):
# zipimporter's loader.archive points to the .egg or .zip file.
filename = loader.archive
else:
# At least one loader is missing both get_filename and archive:
# Google App Engine's HardenedModulesHook, use __file__.
filename = importlib.import_module(root_mod_name).__file__
package_path = os.path.abspath(os.path.dirname(filename))
# If the imported name is a package, filename is currently pointing
# to the root of the package, need to get the current directory.
if _matching_loader_thinks_module_is_package(loader, root_mod_name):
package_path = os.path.dirname(package_path)
return package_path
def find_package(import_name):
"""Find the prefix that a package is installed under, and the path
that it would be imported from.
The prefix is the directory containing the standard directory
hierarchy (lib, bin, etc.). If the package is not installed to the
system (:attr:`sys.prefix`) or a virtualenv (``site-packages``),
``None`` is returned.
The path is the entry in :attr:`sys.path` that contains the package
for import. If the package is not installed, it's assumed that the
package was imported from the current working directory.
"""
root_mod_name, _, _ = import_name.partition(".")
package_path = _find_package_path(root_mod_name)
py_prefix = os.path.abspath(sys.prefix)
# installed to the system
if package_path.startswith(py_prefix):
return py_prefix, package_path
site_parent, site_folder = os.path.split(package_path)
# installed to a virtualenv
if site_folder.lower() == "site-packages":
parent, folder = os.path.split(site_parent)
# Windows (prefix/lib/site-packages)
if folder.lower() == "lib":
return parent, package_path
# Unix (prefix/lib/pythonX.Y/site-packages)
if os.path.basename(parent).lower() == "lib":
return os.path.dirname(parent), package_path
# something else (prefix/site-packages)
return site_parent, package_path
# not installed
return None, package_path