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gh-85133: os docs: Add that getenv uses os.environ (#91874)

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Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
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slateny 2022-05-02 07:43:32 -07:00 • committed by GitHub
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Doc/library/os.rst
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@ -177,8 +177,8 @@ process and user.
This mapping is captured the first time the :mod:`os` module is imported, This mapping is captured the first time the :mod:`os` module is imported,
typically during Python startup as part of processing :file:`site.py`. Changes typically during Python startup as part of processing :file:`site.py`. Changes
to the environment made after this time are not reflected in ``os.environ``, to the environment made after this time are not reflected in :data:`os.environ`,
except for changes made by modifying ``os.environ`` directly. except for changes made by modifying :data:`os.environ` directly.
This mapping may be used to modify the environment as well as query the This mapping may be used to modify the environment as well as query the
environment. :func:`putenv` will be called automatically when the mapping environment. :func:`putenv` will be called automatically when the mapping
@ -190,8 +190,8 @@ process and user.
.. note:: .. note::
Calling :func:`putenv` directly does not change ``os.environ``, so it's better Calling :func:`putenv` directly does not change :data:`os.environ`, so it's better
to modify ``os.environ``. to modify :data:`os.environ`.
.. note:: .. note::
@ -201,7 +201,7 @@ process and user.
You can delete items in this mapping to unset environment variables. You can delete items in this mapping to unset environment variables.
:func:`unsetenv` will be called automatically when an item is deleted from :func:`unsetenv` will be called automatically when an item is deleted from
``os.environ``, and when one of the :meth:`pop` or :meth:`clear` methods is :data:`os.environ`, and when one of the :meth:`pop` or :meth:`clear` methods is
called. called.
.. versionchanged:: 3.9 .. versionchanged:: 3.9
@ -292,7 +292,10 @@ process and user.
.. function:: getenv(key, default=None) .. function:: getenv(key, default=None)
Return the value of the environment variable *key* if it exists, or Return the value of the environment variable *key* if it exists, or
*default* if it doesn't. *key*, *default* and the result are str. *default* if it doesn't. *key*, *default* and the result are str. Note that
since :func:`getenv` uses :data:`os.environ`, the mapping of :func:`getenv` is
similarly also captured on import, and the function may not reflect
future environment changes.
On Unix, keys and values are decoded with :func:`sys.getfilesystemencoding` On Unix, keys and values are decoded with :func:`sys.getfilesystemencoding`
and ``'surrogateescape'`` error handler. Use :func:`os.getenvb` if you and ``'surrogateescape'`` error handler. Use :func:`os.getenvb` if you
@ -304,7 +307,11 @@ process and user.
.. function:: getenvb(key, default=None) .. function:: getenvb(key, default=None)
Return the value of the environment variable *key* if it exists, or Return the value of the environment variable *key* if it exists, or
*default* if it doesn't. *key*, *default* and the result are bytes. *default* if it doesn't. *key*, *default* and the result are bytes. Note that
since :func:`getenvb` uses :data:`os.environb`, the mapping of :func:`getenvb` is
similarly also captured on import, and the function may not reflect
future environment changes.
:func:`getenvb` is only available if :data:`supports_bytes_environ` :func:`getenvb` is only available if :data:`supports_bytes_environ`
is ``True``. is ``True``.
@ -511,10 +518,11 @@ process and user.
changes to the environment affect subprocesses started with :func:`os.system`, changes to the environment affect subprocesses started with :func:`os.system`,
:func:`popen` or :func:`fork` and :func:`execv`. :func:`popen` or :func:`fork` and :func:`execv`.
Assignments to items in ``os.environ`` are automatically translated into Assignments to items in :data:`os.environ` are automatically translated into
corresponding calls to :func:`putenv`; however, calls to :func:`putenv` corresponding calls to :func:`putenv`; however, calls to :func:`putenv`
don't update ``os.environ``, so it is actually preferable to assign to items don't update :data:`os.environ`, so it is actually preferable to assign to items
of ``os.environ``. of :data:`os.environ`. This also applies to :func:`getenv` and :func:`getenvb`, which
respectively use :data:`os.environ` and :data:`os.environb` in their implementations.
.. note:: .. note::
@ -713,10 +721,10 @@ process and user.
environment affect subprocesses started with :func:`os.system`, :func:`popen` or environment affect subprocesses started with :func:`os.system`, :func:`popen` or
:func:`fork` and :func:`execv`. :func:`fork` and :func:`execv`.
Deletion of items in ``os.environ`` is automatically translated into a Deletion of items in :data:`os.environ` is automatically translated into a
corresponding call to :func:`unsetenv`; however, calls to :func:`unsetenv` corresponding call to :func:`unsetenv`; however, calls to :func:`unsetenv`
don't update ``os.environ``, so it is actually preferable to delete items of don't update :data:`os.environ`, so it is actually preferable to delete items of
``os.environ``. :data:`os.environ`.
.. audit-event:: os.unsetenv key os.unsetenv .. audit-event:: os.unsetenv key os.unsetenv