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[3.12] Docs: Update and proofread library/venv.rst (GH-124121) #124680

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128 changes: 119 additions & 9 deletions Doc/library/venv.rst
Original file line number Diff line number Diff line change
Expand Up @@ -37,14 +37,14 @@ A virtual environment is (amongst other things):
are by default isolated from software in other virtual environments and Python
interpreters and libraries installed in the operating system.

* Contained in a directory, conventionally either named ``venv`` or ``.venv`` in
* Contained in a directory, conventionally named ``.venv`` or ``venv`` in
the project directory, or under a container directory for lots of virtual
environments, such as ``~/.virtualenvs``.

* Not checked into source control systems such as Git.

* Considered as disposable -- it should be simple to delete and recreate it from
scratch. You don't place any project code in the environment
scratch. You don't place any project code in the environment.

* Not considered as movable or copyable -- you just recreate the same
environment in the target location.
Expand All @@ -61,7 +61,117 @@ See :pep:`405` for more background on Python virtual environments.
Creating virtual environments
-----------------------------

.. include:: /using/venv-create.inc
:ref:`Virtual environments <venv-def>` are created by executing the ``venv``
module:

.. code-block:: shell

python -m venv /path/to/new/virtual/environment

This creates the target directory (including parent directories as needed)
and places a :file:`pyvenv.cfg` file in it with a ``home`` key
pointing to the Python installation from which the command was run.
It also creates a :file:`bin` (or :file:`Scripts` on Windows) subdirectory
containing a copy or symlink of the Python executable
(as appropriate for the platform or arguments used at environment creation time).
It also creates a :file:`lib/pythonX.Y/site-packages` subdirectory
(on Windows, this is :file:`Lib\site-packages`).
If an existing directory is specified, it will be re-used.

.. versionchanged:: 3.5
The use of ``venv`` is now recommended for creating virtual environments.

.. deprecated-removed:: 3.6 3.8
:program:`pyvenv` was the recommended tool for creating virtual environments
for Python 3.3 and 3.4, and replaced in 3.5 by executing ``venv`` directly.

.. highlight:: none

On Windows, invoke the ``venv`` command as follows:

.. code-block:: ps1con

PS> python -m venv C:\path\to\new\virtual\environment

The command, if run with ``-h``, will show the available options::

usage: venv [-h] [--system-site-packages] [--symlinks | --copies] [--clear]
[--upgrade] [--without-pip] [--prompt PROMPT] [--upgrade-deps]
ENV_DIR [ENV_DIR ...]

Creates virtual Python environments in one or more target directories.

positional arguments:
ENV_DIR A directory to create the environment in.

options:
-h, --help show this help message and exit
--system-site-packages
Give the virtual environment access to the system
site-packages dir.
--symlinks Try to use symlinks rather than copies, when
symlinks are not the default for the platform.
--copies Try to use copies rather than symlinks, even when
symlinks are the default for the platform.
--clear Delete the contents of the environment directory
if it already exists, before environment creation.
--upgrade Upgrade the environment directory to use this
version of Python, assuming Python has been
upgraded in-place.
--without-pip Skips installing or upgrading pip in the virtual
environment (pip is bootstrapped by default)
--prompt PROMPT Provides an alternative prompt prefix for this
environment.
--upgrade-deps Upgrade core dependencies (pip) to the latest
version in PyPI

Once an environment has been created, you may wish to activate it, e.g. by
sourcing an activate script in its bin directory.


.. versionchanged:: 3.4
Installs pip by default, added the ``--without-pip`` and ``--copies``
options.

.. versionchanged:: 3.4
In earlier versions, if the target directory already existed, an error was
raised, unless the ``--clear`` or ``--upgrade`` option was provided.

.. versionchanged:: 3.9
Add ``--upgrade-deps`` option to upgrade pip + setuptools to the latest on PyPI.

.. versionchanged:: 3.12

``setuptools`` is no longer a core venv dependency.

.. note::
While symlinks are supported on Windows, they are not recommended. Of
particular note is that double-clicking ``python.exe`` in File Explorer
will resolve the symlink eagerly and ignore the virtual environment.

.. note::
On Microsoft Windows, it may be required to enable the ``Activate.ps1``
script by setting the execution policy for the user. You can do this by
issuing the following PowerShell command:

.. code-block:: powershell

PS C:\> Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

See `About Execution Policies
<https://go.microsoft.com/fwlink/?LinkID=135170>`_
for more information.

The created :file:`pyvenv.cfg` file also includes the
``include-system-site-packages`` key, set to ``true`` if ``venv`` is
run with the ``--system-site-packages`` option, ``false`` otherwise.

Unless the ``--without-pip`` option is given, :mod:`ensurepip` will be
invoked to bootstrap ``pip`` into the virtual environment.

Multiple paths can be given to ``venv``, in which case an identical virtual
environment will be created, according to the given options, at each provided
path.

.. _venv-explanation:

Expand Down Expand Up @@ -117,7 +227,7 @@ should be runnable without activating it.

In order to achieve this, scripts installed into virtual environments have
a "shebang" line which points to the environment's Python interpreter,
i.e. :samp:`#!/{<path-to-venv>}/bin/python`.
:samp:`#!/{<path-to-venv>}/bin/python`.
This means that the script will run with that interpreter regardless of the
value of :envvar:`PATH`. On Windows, "shebang" line processing is supported if
you have the :ref:`launcher` installed. Thus, double-clicking an installed
Expand Down Expand Up @@ -335,8 +445,8 @@ creation according to their needs, the :class:`EnvBuilder` class.
.. method:: install_scripts(context, path)

*path* is the path to a directory that should contain subdirectories
"common", "posix", "nt", each containing scripts destined for the bin
directory in the environment. The contents of "common" and the
``common``, ``posix``, ``nt``; each containing scripts destined for the
``bin`` directory in the environment. The contents of ``common`` and the
directory corresponding to :data:`os.name` are copied after some text
replacement of placeholders:

Expand Down Expand Up @@ -370,13 +480,13 @@ There is also a module-level convenience function:
.. versionadded:: 3.3

.. versionchanged:: 3.4
Added the ``with_pip`` parameter
Added the *with_pip* parameter

.. versionchanged:: 3.6
Added the ``prompt`` parameter
Added the *prompt* parameter

.. versionchanged:: 3.9
Added the ``upgrade_deps`` parameter
Added the *upgrade_deps* parameter

An example of extending ``EnvBuilder``
--------------------------------------
Expand Down
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