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gh-100176: Remove redundant compat code for Python 3.2 and older Python 3.2 has been EOL since 2016-02-20 and 2.7 since 2020-01-01, so we can remove this old compatibility check and unindent the old else-block. Also, in the unindented block, replace a .format() call with an f-string. Plus similar changes in the documentation.
578 lines
25 KiB
ReStructuredText
578 lines
25 KiB
ReStructuredText
:mod:`venv` --- Creation of virtual environments
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================================================
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.. module:: venv
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:synopsis: Creation of virtual environments.
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.. moduleauthor:: Vinay Sajip <vinay_sajip@yahoo.co.uk>
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.. sectionauthor:: Vinay Sajip <vinay_sajip@yahoo.co.uk>
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.. versionadded:: 3.3
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**Source code:** :source:`Lib/venv/`
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.. index:: pair: Environments; virtual
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--------------
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.. _venv-def:
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.. _venv-intro:
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The :mod:`!venv` module supports creating lightweight "virtual environments",
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each with their own independent set of Python packages installed in
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their :mod:`site` directories.
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A virtual environment is created on top of an existing
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Python installation, known as the virtual environment's "base" Python, and may
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optionally be isolated from the packages in the base environment,
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so only those explicitly installed in the virtual environment are available.
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When used from within a virtual environment, common installation tools such as
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`pip`_ will install Python packages into a virtual environment
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without needing to be told to do so explicitly.
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See :pep:`405` for more background on Python virtual environments.
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.. seealso::
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`Python Packaging User Guide: Creating and using virtual environments
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<https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/#creating-a-virtual-environment>`__
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.. include:: ../includes/wasm-notavail.rst
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Creating virtual environments
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-----------------------------
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.. include:: /using/venv-create.inc
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.. _venv-explanation:
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How venvs work
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--------------
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When a Python interpreter is running from a virtual environment,
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:data:`sys.prefix` and :data:`sys.exec_prefix`
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point to the directories of the virtual environment,
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whereas :data:`sys.base_prefix` and :data:`sys.base_exec_prefix`
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point to those of the base Python used to create the environment.
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It is sufficient to check
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``sys.prefix == sys.base_prefix`` to determine if the current interpreter is
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running from a virtual environment.
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A virtual environment may be "activated" using a script in its binary directory
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(``bin`` on POSIX; ``Scripts`` on Windows).
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This will prepend that directory to your :envvar:`!PATH`, so that running
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:program:`!python` will invoke the environment's Python interpreter
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and you can run installed scripts without having to use their full path.
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The invocation of the activation script is platform-specific
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(:samp:`{<venv>}` must be replaced by the path to the directory
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containing the virtual environment):
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+-------------+------------+--------------------------------------------------+
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| Platform | Shell | Command to activate virtual environment |
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+=============+============+==================================================+
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| POSIX | bash/zsh | :samp:`$ source {<venv>}/bin/activate` |
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| +------------+--------------------------------------------------+
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| | fish | :samp:`$ source {<venv>}/bin/activate.fish` |
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| +------------+--------------------------------------------------+
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| | csh/tcsh | :samp:`$ source {<venv>}/bin/activate.csh` |
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| +------------+--------------------------------------------------+
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| | PowerShell | :samp:`$ {<venv>}/bin/Activate.ps1` |
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+-------------+------------+--------------------------------------------------+
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| Windows | cmd.exe | :samp:`C:\\> {<venv>}\\Scripts\\activate.bat` |
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| +------------+--------------------------------------------------+
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| | PowerShell | :samp:`PS C:\\> {<venv>}\\Scripts\\Activate.ps1` |
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+-------------+------------+--------------------------------------------------+
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.. versionadded:: 3.4
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:program:`!fish` and :program:`!csh` activation scripts.
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.. versionadded:: 3.8
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PowerShell activation scripts installed under POSIX for PowerShell Core
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support.
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You don't specifically *need* to activate a virtual environment,
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as you can just specify the full path to that environment's
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Python interpreter when invoking Python.
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Furthermore, all scripts installed in the environment
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should be runnable without activating it.
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In order to achieve this, scripts installed into virtual environments have
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a "shebang" line which points to the environment's Python interpreter,
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i.e. :samp:`#!/{<path-to-venv>}/bin/python`.
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This means that the script will run with that interpreter regardless of the
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value of :envvar:`!PATH`. On Windows, "shebang" line processing is supported if
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you have the :ref:`launcher` installed. Thus, double-clicking an installed
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script in a Windows Explorer window should run it with the correct interpreter
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without the environment needing to be activated or on the :envvar:`!PATH`.
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When a virtual environment has been activated, the :envvar:`!VIRTUAL_ENV`
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environment variable is set to the path of the environment.
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Since explicitly activating a virtual environment is not required to use it,
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:envvar:`!VIRTUAL_ENV` cannot be relied upon to determine
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whether a virtual environment is being used.
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.. warning:: Because scripts installed in environments should not expect the
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environment to be activated, their shebang lines contain the absolute paths
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to their environment's interpreters. Because of this, environments are
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inherently non-portable, in the general case. You should always have a
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simple means of recreating an environment (for example, if you have a
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requirements file ``requirements.txt``, you can invoke ``pip install -r
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requirements.txt`` using the environment's ``pip`` to install all of the
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packages needed by the environment). If for any reason you need to move the
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environment to a new location, you should recreate it at the desired
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location and delete the one at the old location. If you move an environment
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because you moved a parent directory of it, you should recreate the
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environment in its new location. Otherwise, software installed into the
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environment may not work as expected.
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You can deactivate a virtual environment by typing ``deactivate`` in your shell.
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The exact mechanism is platform-specific and is an internal implementation
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detail (typically, a script or shell function will be used).
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.. _venv-api:
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API
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---
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.. highlight:: python
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The high-level method described above makes use of a simple API which provides
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mechanisms for third-party virtual environment creators to customize environment
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creation according to their needs, the :class:`EnvBuilder` class.
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.. class:: EnvBuilder(system_site_packages=False, clear=False, \
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symlinks=False, upgrade=False, with_pip=False, \
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prompt=None, upgrade_deps=False)
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The :class:`EnvBuilder` class accepts the following keyword arguments on
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instantiation:
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* ``system_site_packages`` -- a Boolean value indicating that the system Python
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site-packages should be available to the environment (defaults to ``False``).
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* ``clear`` -- a Boolean value which, if true, will delete the contents of
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any existing target directory, before creating the environment.
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* ``symlinks`` -- a Boolean value indicating whether to attempt to symlink the
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Python binary rather than copying.
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* ``upgrade`` -- a Boolean value which, if true, will upgrade an existing
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environment with the running Python - for use when that Python has been
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upgraded in-place (defaults to ``False``).
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* ``with_pip`` -- a Boolean value which, if true, ensures pip is
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installed in the virtual environment. This uses :mod:`ensurepip` with
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the ``--default-pip`` option.
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* ``prompt`` -- a String to be used after virtual environment is activated
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(defaults to ``None`` which means directory name of the environment would
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be used). If the special string ``"."`` is provided, the basename of the
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current directory is used as the prompt.
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* ``upgrade_deps`` -- Update the base venv modules to the latest on PyPI
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.. versionchanged:: 3.4
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Added the ``with_pip`` parameter
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.. versionadded:: 3.6
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Added the ``prompt`` parameter
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.. versionadded:: 3.9
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Added the ``upgrade_deps`` parameter
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Creators of third-party virtual environment tools will be free to use the
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provided :class:`EnvBuilder` class as a base class.
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The returned env-builder is an object which has a method, ``create``:
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.. method:: create(env_dir)
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Create a virtual environment by specifying the target directory
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(absolute or relative to the current directory) which is to contain the
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virtual environment. The ``create`` method will either create the
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environment in the specified directory, or raise an appropriate
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exception.
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The ``create`` method of the :class:`EnvBuilder` class illustrates the
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hooks available for subclass customization::
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def create(self, env_dir):
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"""
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Create a virtualized Python environment in a directory.
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env_dir is the target directory to create an environment in.
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"""
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env_dir = os.path.abspath(env_dir)
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context = self.ensure_directories(env_dir)
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self.create_configuration(context)
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self.setup_python(context)
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self.setup_scripts(context)
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self.post_setup(context)
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Each of the methods :meth:`ensure_directories`,
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:meth:`create_configuration`, :meth:`setup_python`,
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:meth:`setup_scripts` and :meth:`post_setup` can be overridden.
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.. method:: ensure_directories(env_dir)
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Creates the environment directory and all necessary subdirectories that
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don't already exist, and returns a context object. This context object
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is just a holder for attributes (such as paths) for use by the other
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methods. If the :class:`EnvBuilder` is created with the arg
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``clear=True``, contents of the environment directory will be cleared
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and then all necessary subdirectories will be recreated.
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The returned context object is a :class:`types.SimpleNamespace` with the
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following attributes:
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* ``env_dir`` - The location of the virtual environment. Used for
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``__VENV_DIR__`` in activation scripts (see :meth:`install_scripts`).
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* ``env_name`` - The name of the virtual environment. Used for
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``__VENV_NAME__`` in activation scripts (see :meth:`install_scripts`).
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* ``prompt`` - The prompt to be used by the activation scripts. Used for
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``__VENV_PROMPT__`` in activation scripts (see :meth:`install_scripts`).
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* ``executable`` - The underlying Python executable used by the virtual
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environment. This takes into account the case where a virtual environment
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is created from another virtual environment.
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* ``inc_path`` - The include path for the virtual environment.
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* ``lib_path`` - The purelib path for the virtual environment.
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* ``bin_path`` - The script path for the virtual environment.
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* ``bin_name`` - The name of the script path relative to the virtual
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environment location. Used for ``__VENV_BIN_NAME__`` in activation
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scripts (see :meth:`install_scripts`).
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* ``env_exe`` - The name of the Python interpreter in the virtual
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environment. Used for ``__VENV_PYTHON__`` in activation scripts
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(see :meth:`install_scripts`).
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* ``env_exec_cmd`` - The name of the Python interpreter, taking into
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account filesystem redirections. This can be used to run Python in
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the virtual environment.
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.. versionchanged:: 3.12
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The attribute ``lib_path`` was added to the context, and the context
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object was documented.
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.. versionchanged:: 3.11
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The *venv*
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:ref:`sysconfig installation scheme <installation_paths>`
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is used to construct the paths of the created directories.
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.. method:: create_configuration(context)
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Creates the ``pyvenv.cfg`` configuration file in the environment.
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.. method:: setup_python(context)
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Creates a copy or symlink to the Python executable in the environment.
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On POSIX systems, if a specific executable ``python3.x`` was used,
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symlinks to ``python`` and ``python3`` will be created pointing to that
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executable, unless files with those names already exist.
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.. method:: setup_scripts(context)
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Installs activation scripts appropriate to the platform into the virtual
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environment.
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.. method:: upgrade_dependencies(context)
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Upgrades the core venv dependency packages (currently ``pip`` and
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``setuptools``) in the environment. This is done by shelling out to the
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``pip`` executable in the environment.
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.. versionadded:: 3.9
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.. method:: post_setup(context)
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A placeholder method which can be overridden in third party
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implementations to pre-install packages in the virtual environment or
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perform other post-creation steps.
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.. versionchanged:: 3.7.2
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Windows now uses redirector scripts for ``python[w].exe`` instead of
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copying the actual binaries. In 3.7.2 only :meth:`setup_python` does
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nothing unless running from a build in the source tree.
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.. versionchanged:: 3.7.3
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Windows copies the redirector scripts as part of :meth:`setup_python`
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instead of :meth:`setup_scripts`. This was not the case in 3.7.2.
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When using symlinks, the original executables will be linked.
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In addition, :class:`EnvBuilder` provides this utility method that can be
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called from :meth:`setup_scripts` or :meth:`post_setup` in subclasses to
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assist in installing custom scripts into the virtual environment.
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.. method:: install_scripts(context, path)
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*path* is the path to a directory that should contain subdirectories
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"common", "posix", "nt", each containing scripts destined for the bin
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directory in the environment. The contents of "common" and the
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directory corresponding to :data:`os.name` are copied after some text
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replacement of placeholders:
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* ``__VENV_DIR__`` is replaced with the absolute path of the environment
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directory.
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* ``__VENV_NAME__`` is replaced with the environment name (final path
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segment of environment directory).
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* ``__VENV_PROMPT__`` is replaced with the prompt (the environment
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name surrounded by parentheses and with a following space)
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* ``__VENV_BIN_NAME__`` is replaced with the name of the bin directory
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(either ``bin`` or ``Scripts``).
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* ``__VENV_PYTHON__`` is replaced with the absolute path of the
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environment's executable.
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The directories are allowed to exist (for when an existing environment
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is being upgraded).
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There is also a module-level convenience function:
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.. function:: create(env_dir, system_site_packages=False, clear=False, \
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symlinks=False, with_pip=False, prompt=None, \
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upgrade_deps=False)
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Create an :class:`EnvBuilder` with the given keyword arguments, and call its
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:meth:`~EnvBuilder.create` method with the *env_dir* argument.
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.. versionadded:: 3.3
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.. versionchanged:: 3.4
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Added the ``with_pip`` parameter
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.. versionchanged:: 3.6
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Added the ``prompt`` parameter
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.. versionchanged:: 3.9
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Added the ``upgrade_deps`` parameter
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An example of extending ``EnvBuilder``
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--------------------------------------
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The following script shows how to extend :class:`EnvBuilder` by implementing a
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subclass which installs setuptools and pip into a created virtual environment::
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import os
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import os.path
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from subprocess import Popen, PIPE
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import sys
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from threading import Thread
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from urllib.parse import urlparse
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from urllib.request import urlretrieve
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import venv
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class ExtendedEnvBuilder(venv.EnvBuilder):
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"""
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This builder installs setuptools and pip so that you can pip or
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easy_install other packages into the created virtual environment.
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:param nodist: If true, setuptools and pip are not installed into the
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created virtual environment.
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:param nopip: If true, pip is not installed into the created
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virtual environment.
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:param progress: If setuptools or pip are installed, the progress of the
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installation can be monitored by passing a progress
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callable. If specified, it is called with two
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arguments: a string indicating some progress, and a
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context indicating where the string is coming from.
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The context argument can have one of three values:
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'main', indicating that it is called from virtualize()
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itself, and 'stdout' and 'stderr', which are obtained
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by reading lines from the output streams of a subprocess
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which is used to install the app.
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If a callable is not specified, default progress
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information is output to sys.stderr.
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"""
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def __init__(self, *args, **kwargs):
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self.nodist = kwargs.pop('nodist', False)
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self.nopip = kwargs.pop('nopip', False)
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self.progress = kwargs.pop('progress', None)
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self.verbose = kwargs.pop('verbose', False)
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super().__init__(*args, **kwargs)
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def post_setup(self, context):
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"""
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Set up any packages which need to be pre-installed into the
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virtual environment being created.
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:param context: The information for the virtual environment
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creation request being processed.
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"""
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os.environ['VIRTUAL_ENV'] = context.env_dir
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if not self.nodist:
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self.install_setuptools(context)
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# Can't install pip without setuptools
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if not self.nopip and not self.nodist:
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self.install_pip(context)
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def reader(self, stream, context):
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"""
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Read lines from a subprocess' output stream and either pass to a progress
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callable (if specified) or write progress information to sys.stderr.
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"""
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progress = self.progress
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while True:
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s = stream.readline()
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if not s:
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break
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if progress is not None:
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progress(s, context)
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else:
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if not self.verbose:
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sys.stderr.write('.')
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else:
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sys.stderr.write(s.decode('utf-8'))
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sys.stderr.flush()
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stream.close()
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def install_script(self, context, name, url):
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_, _, path, _, _, _ = urlparse(url)
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fn = os.path.split(path)[-1]
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binpath = context.bin_path
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distpath = os.path.join(binpath, fn)
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# Download script into the virtual environment's binaries folder
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urlretrieve(url, distpath)
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progress = self.progress
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if self.verbose:
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term = '\n'
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else:
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term = ''
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if progress is not None:
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progress('Installing %s ...%s' % (name, term), 'main')
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else:
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sys.stderr.write('Installing %s ...%s' % (name, term))
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sys.stderr.flush()
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# Install in the virtual environment
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args = [context.env_exe, fn]
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p = Popen(args, stdout=PIPE, stderr=PIPE, cwd=binpath)
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t1 = Thread(target=self.reader, args=(p.stdout, 'stdout'))
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t1.start()
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t2 = Thread(target=self.reader, args=(p.stderr, 'stderr'))
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t2.start()
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p.wait()
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t1.join()
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t2.join()
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if progress is not None:
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progress('done.', 'main')
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else:
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sys.stderr.write('done.\n')
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# Clean up - no longer needed
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os.unlink(distpath)
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def install_setuptools(self, context):
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"""
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Install setuptools in the virtual environment.
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:param context: The information for the virtual environment
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creation request being processed.
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"""
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url = 'https://bitbucket.org/pypa/setuptools/downloads/ez_setup.py'
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self.install_script(context, 'setuptools', url)
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# clear up the setuptools archive which gets downloaded
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pred = lambda o: o.startswith('setuptools-') and o.endswith('.tar.gz')
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files = filter(pred, os.listdir(context.bin_path))
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for f in files:
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f = os.path.join(context.bin_path, f)
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os.unlink(f)
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def install_pip(self, context):
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"""
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Install pip in the virtual environment.
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:param context: The information for the virtual environment
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creation request being processed.
|
|
"""
|
|
url = 'https://bootstrap.pypa.io/get-pip.py'
|
|
self.install_script(context, 'pip', url)
|
|
|
|
|
|
def main(args=None):
|
|
import argparse
|
|
|
|
parser = argparse.ArgumentParser(prog=__name__,
|
|
description='Creates virtual Python '
|
|
'environments in one or '
|
|
'more target '
|
|
'directories.')
|
|
parser.add_argument('dirs', metavar='ENV_DIR', nargs='+',
|
|
help='A directory in which to create the '
|
|
'virtual environment.')
|
|
parser.add_argument('--no-setuptools', default=False,
|
|
action='store_true', dest='nodist',
|
|
help="Don't install setuptools or pip in the "
|
|
"virtual environment.")
|
|
parser.add_argument('--no-pip', default=False,
|
|
action='store_true', dest='nopip',
|
|
help="Don't install pip in the virtual "
|
|
"environment.")
|
|
parser.add_argument('--system-site-packages', default=False,
|
|
action='store_true', dest='system_site',
|
|
help='Give the virtual environment access to the '
|
|
'system site-packages dir.')
|
|
if os.name == 'nt':
|
|
use_symlinks = False
|
|
else:
|
|
use_symlinks = True
|
|
parser.add_argument('--symlinks', default=use_symlinks,
|
|
action='store_true', dest='symlinks',
|
|
help='Try to use symlinks rather than copies, '
|
|
'when symlinks are not the default for '
|
|
'the platform.')
|
|
parser.add_argument('--clear', default=False, action='store_true',
|
|
dest='clear', help='Delete the contents of the '
|
|
'virtual environment '
|
|
'directory if it already '
|
|
'exists, before virtual '
|
|
'environment creation.')
|
|
parser.add_argument('--upgrade', default=False, action='store_true',
|
|
dest='upgrade', help='Upgrade the virtual '
|
|
'environment directory to '
|
|
'use this version of '
|
|
'Python, assuming Python '
|
|
'has been upgraded '
|
|
'in-place.')
|
|
parser.add_argument('--verbose', default=False, action='store_true',
|
|
dest='verbose', help='Display the output '
|
|
'from the scripts which '
|
|
'install setuptools and pip.')
|
|
options = parser.parse_args(args)
|
|
if options.upgrade and options.clear:
|
|
raise ValueError('you cannot supply --upgrade and --clear together.')
|
|
builder = ExtendedEnvBuilder(system_site_packages=options.system_site,
|
|
clear=options.clear,
|
|
symlinks=options.symlinks,
|
|
upgrade=options.upgrade,
|
|
nodist=options.nodist,
|
|
nopip=options.nopip,
|
|
verbose=options.verbose)
|
|
for d in options.dirs:
|
|
builder.create(d)
|
|
|
|
if __name__ == '__main__':
|
|
rc = 1
|
|
try:
|
|
main()
|
|
rc = 0
|
|
except Exception as e:
|
|
print('Error: %s' % e, file=sys.stderr)
|
|
sys.exit(rc)
|
|
|
|
|
|
This script is also available for download `online
|
|
<https://gist.github.com/vsajip/4673395>`_.
|
|
|
|
|
|
.. _setuptools: https://pypi.org/project/setuptools/
|
|
.. _pip: https://pypi.org/project/pip/
|