429 lines
19 KiB
ReStructuredText
429 lines
19 KiB
ReStructuredText
:mod:`venv` --- Creation of virtual environments
|
|
================================================
|
|
|
|
.. module:: venv
|
|
:synopsis: Creation of virtual environments.
|
|
.. moduleauthor:: Vinay Sajip <vinay_sajip@yahoo.co.uk>
|
|
.. sectionauthor:: Vinay Sajip <vinay_sajip@yahoo.co.uk>
|
|
|
|
|
|
.. index:: pair: Environments; virtual
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
**Source code:** :source:`Lib/venv`
|
|
|
|
--------------
|
|
|
|
The :mod:`venv` module provides support for creating lightweight "virtual
|
|
environments" with their own site directories, optionally isolated from system
|
|
site directories. Each virtual environment has its own Python binary (allowing
|
|
creation of environments with various Python versions) and can have its own
|
|
independent set of installed Python packages in its site directories.
|
|
|
|
See :pep:`405` for more information about Python virtual environments.
|
|
|
|
Creating virtual environments
|
|
-----------------------------
|
|
|
|
.. include:: /using/venv-create.inc
|
|
|
|
|
|
.. _venv-def:
|
|
|
|
.. note:: A virtual environment (also called a ``venv``) is a Python
|
|
environment such that the Python interpreter, libraries and scripts
|
|
installed into it are isolated from those installed in other virtual
|
|
environments, and (by default) any libraries installed in a "system" Python,
|
|
i.e. one which is installed as part of your operating system.
|
|
|
|
A venv is a directory tree which contains Python executable files and
|
|
other files which indicate that it is a venv.
|
|
|
|
Common installation tools such as ``Distribute`` and ``pip`` work as
|
|
expected with venvs - i.e. when a venv is active, they install Python
|
|
packages into the venv without needing to be told to do so explicitly.
|
|
Of course, you need to install them into the venv first: this could be
|
|
done by running ``distribute_setup.py`` with the venv activated,
|
|
followed by running ``easy_install pip``. Alternatively, you could download
|
|
the source tarballs and run ``python setup.py install`` after unpacking,
|
|
with the venv activated.
|
|
|
|
When a venv is active (i.e. the venv's Python interpreter is running), the
|
|
attributes :attr:`sys.prefix` and :attr:`sys.exec_prefix` point to the base
|
|
directory of the venv, whereas :attr:`sys.base_prefix` and
|
|
:attr:`sys.base_exec_prefix` point to the non-venv Python installation
|
|
which was used to create the venv. If a venv is not active, then
|
|
:attr:`sys.prefix` is the same as :attr:`sys.base_prefix` and
|
|
:attr:`sys.exec_prefix` is the same as :attr:`sys.base_exec_prefix` (they
|
|
all point to a non-venv Python installation).
|
|
|
|
When a venv is active, any options that change the installation path will be
|
|
ignored from all distutils configuration files to prevent projects being
|
|
inadvertently installed outside of the virtual environment.
|
|
|
|
When working in a command shell, users can make a venv active by running an
|
|
``activate`` script in the venv's executables directory (the precise filename
|
|
is shell-dependent), which prepends the venv's directory for executables to
|
|
the ``PATH`` environment variable for the running shell. There should be no
|
|
need in other circumstances to activate a venv -- scripts installed into
|
|
venvs have a shebang line which points to the venv's Python interpreter. This
|
|
means that the script will run with that interpreter regardless of the value
|
|
of ``PATH``. On Windows, shebang line processing is supported if you have the
|
|
Python Launcher for Windows installed (this was added to Python in 3.3 - see
|
|
:pep:`397` for more details). Thus, double-clicking an installed script in
|
|
a Windows Explorer window should run the script with the correct interpreter
|
|
without there needing to be any reference to its venv in ``PATH``.
|
|
|
|
|
|
API
|
|
---
|
|
|
|
.. highlight:: python
|
|
|
|
The high-level method described above makes use of a simple API which provides
|
|
mechanisms for third-party virtual environment creators to customize environment
|
|
creation according to their needs, the :class:`EnvBuilder` class.
|
|
|
|
.. class:: EnvBuilder(system_site_packages=False, clear=False, symlinks=False, upgrade=False)
|
|
|
|
The :class:`EnvBuilder` class accepts the following keyword arguments on
|
|
instantiation:
|
|
|
|
* ``system_site_packages`` -- a Boolean value indicating that the system Python
|
|
site-packages should be available to the environment (defaults to ``False``).
|
|
|
|
* ``clear`` -- a Boolean value which, if True, will delete the contents of
|
|
any existing target directory, before creating the environment.
|
|
|
|
* ``symlinks`` -- a Boolean value indicating whether to attempt to symlink the
|
|
Python binary (and any necessary DLLs or other binaries,
|
|
e.g. ``pythonw.exe``), rather than copying. Defaults to ``True`` on Linux and
|
|
Unix systems, but ``False`` on Windows.
|
|
|
|
* ``upgrade`` -- a Boolean value which, if True, will upgrade an existing
|
|
environment with the running Python - for use when that Python has been
|
|
upgraded in-place (defaults to ``False``).
|
|
|
|
|
|
Creators of third-party virtual environment tools will be free to use the
|
|
provided ``EnvBuilder`` class as a base class.
|
|
|
|
The returned env-builder is an object which has a method, ``create``:
|
|
|
|
.. method:: create(env_dir)
|
|
|
|
This method takes as required argument the path (absolute or relative to
|
|
the current directory) of the target directory which is to contain the
|
|
virtual environment. The ``create`` method will either create the
|
|
environment in the specified directory, or raise an appropriate
|
|
exception.
|
|
|
|
The ``create`` method of the ``EnvBuilder`` class illustrates the hooks
|
|
available for subclass customization::
|
|
|
|
def create(self, env_dir):
|
|
"""
|
|
Create a virtualized Python environment in a directory.
|
|
env_dir is the target directory to create an environment in.
|
|
"""
|
|
env_dir = os.path.abspath(env_dir)
|
|
context = self.ensure_directories(env_dir)
|
|
self.create_configuration(context)
|
|
self.setup_python(context)
|
|
self.setup_scripts(context)
|
|
self.post_setup(context)
|
|
|
|
Each of the methods :meth:`ensure_directories`,
|
|
:meth:`create_configuration`, :meth:`setup_python`,
|
|
:meth:`setup_scripts` and :meth:`post_setup` can be overridden.
|
|
|
|
.. method:: ensure_directories(env_dir)
|
|
|
|
Creates the environment directory and all necessary directories, and
|
|
returns a context object. This is just a holder for attributes (such as
|
|
paths), for use by the other methods. The directories are allowed to
|
|
exist already, as long as either ``clear`` or ``upgrade`` were
|
|
specified to allow operating on an existing environment directory.
|
|
|
|
.. method:: create_configuration(context)
|
|
|
|
Creates the ``pyvenv.cfg`` configuration file in the environment.
|
|
|
|
.. method:: setup_python(context)
|
|
|
|
Creates a copy of the Python executable (and, under Windows, DLLs) in
|
|
the environment. On a POSIX system, if a specific executable
|
|
``python3.x`` was used, symlinks to ``python`` and ``python3`` will be
|
|
created pointing to that executable, unless files with those names
|
|
already exist.
|
|
|
|
.. method:: setup_scripts(context)
|
|
|
|
Installs activation scripts appropriate to the platform into the virtual
|
|
environment.
|
|
|
|
.. method:: post_setup(context)
|
|
|
|
A placeholder method which can be overridden in third party
|
|
implementations to pre-install packages in the virtual environment or
|
|
perform other post-creation steps.
|
|
|
|
In addition, :class:`EnvBuilder` provides this utility method that can be
|
|
called from :meth:`setup_scripts` or :meth:`post_setup` in subclasses to
|
|
assist in installing custom scripts into the virtual environment.
|
|
|
|
.. 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
|
|
directory corresponding to :data:`os.name` are copied after some text
|
|
replacement of placeholders:
|
|
|
|
* ``__VENV_DIR__`` is replaced with the absolute path of the environment
|
|
directory.
|
|
|
|
* ``__VENV_NAME__`` is replaced with the environment name (final path
|
|
segment of environment directory).
|
|
|
|
* ``__VENV_PROMPT__`` is replaced with the prompt (the environment
|
|
name surrounded by parentheses and with a following space)
|
|
|
|
* ``__VENV_BIN_NAME__`` is replaced with the name of the bin directory
|
|
(either ``bin`` or ``Scripts``).
|
|
|
|
* ``__VENV_PYTHON__`` is replaced with the absolute path of the
|
|
environment's executable.
|
|
|
|
The directories are allowed to exist (for when an existing environment
|
|
is being upgraded).
|
|
|
|
There is also a module-level convenience function:
|
|
|
|
.. function:: create(env_dir, system_site_packages=False, clear=False, symlinks=False)
|
|
|
|
Create an :class:`EnvBuilder` with the given keyword arguments, and call its
|
|
:meth:`~EnvBuilder.create` method with the *env_dir* argument.
|
|
|
|
An example of extending ``EnvBuilder``
|
|
--------------------------------------
|
|
|
|
The following script shows how to extend :class:`EnvBuilder` by implementing a
|
|
subclass which installs setuptools and pip into a created venv::
|
|
|
|
import os
|
|
import os.path
|
|
from subprocess import Popen, PIPE
|
|
import sys
|
|
from threading import Thread
|
|
from urllib.parse import urlparse
|
|
from urllib.request import urlretrieve
|
|
import venv
|
|
|
|
class ExtendedEnvBuilder(venv.EnvBuilder):
|
|
"""
|
|
This builder installs setuptools and pip so that you can pip or
|
|
easy_install other packages into the created environment.
|
|
|
|
:param nodist: If True, setuptools and pip are not installed into the
|
|
created environment.
|
|
:param nopip: If True, pip is not installed into the created
|
|
environment.
|
|
:param progress: If setuptools or pip are installed, the progress of the
|
|
installation can be monitored by passing a progress
|
|
callable. If specified, it is called with two
|
|
arguments: a string indicating some progress, and a
|
|
context indicating where the string is coming from.
|
|
The context argument can have one of three values:
|
|
'main', indicating that it is called from virtualize()
|
|
itself, and 'stdout' and 'stderr', which are obtained
|
|
by reading lines from the output streams of a subprocess
|
|
which is used to install the app.
|
|
|
|
If a callable is not specified, default progress
|
|
information is output to sys.stderr.
|
|
"""
|
|
|
|
def __init__(self, *args, **kwargs):
|
|
self.nodist = kwargs.pop('nodist', False)
|
|
self.nopip = kwargs.pop('nopip', False)
|
|
self.progress = kwargs.pop('progress', None)
|
|
self.verbose = kwargs.pop('verbose', False)
|
|
super().__init__(*args, **kwargs)
|
|
|
|
def post_setup(self, context):
|
|
"""
|
|
Set up any packages which need to be pre-installed into the
|
|
environment being created.
|
|
|
|
:param context: The information for the environment creation request
|
|
being processed.
|
|
"""
|
|
os.environ['VIRTUAL_ENV'] = context.env_dir
|
|
if not self.nodist:
|
|
self.install_setuptools(context)
|
|
# Can't install pip without setuptools
|
|
if not self.nopip and not self.nodist:
|
|
self.install_pip(context)
|
|
|
|
def reader(self, stream, context):
|
|
"""
|
|
Read lines from a subprocess' output stream and either pass to a progress
|
|
callable (if specified) or write progress information to sys.stderr.
|
|
"""
|
|
progress = self.progress
|
|
while True:
|
|
s = stream.readline()
|
|
if not s:
|
|
break
|
|
if progress is not None:
|
|
progress(s, context)
|
|
else:
|
|
if not self.verbose:
|
|
sys.stderr.write('.')
|
|
else:
|
|
sys.stderr.write(s.decode('utf-8'))
|
|
sys.stderr.flush()
|
|
stream.close()
|
|
|
|
def install_script(self, context, name, url):
|
|
_, _, path, _, _, _ = urlparse(url)
|
|
fn = os.path.split(path)[-1]
|
|
binpath = context.bin_path
|
|
distpath = os.path.join(binpath, fn)
|
|
# Download script into the env's binaries folder
|
|
urlretrieve(url, distpath)
|
|
progress = self.progress
|
|
if self.verbose:
|
|
term = '\n'
|
|
else:
|
|
term = ''
|
|
if progress is not None:
|
|
progress('Installing %s ...%s' % (name, term), 'main')
|
|
else:
|
|
sys.stderr.write('Installing %s ...%s' % (name, term))
|
|
sys.stderr.flush()
|
|
# Install in the env
|
|
args = [context.env_exe, fn]
|
|
p = Popen(args, stdout=PIPE, stderr=PIPE, cwd=binpath)
|
|
t1 = Thread(target=self.reader, args=(p.stdout, 'stdout'))
|
|
t1.start()
|
|
t2 = Thread(target=self.reader, args=(p.stderr, 'stderr'))
|
|
t2.start()
|
|
p.wait()
|
|
t1.join()
|
|
t2.join()
|
|
if progress is not None:
|
|
progress('done.', 'main')
|
|
else:
|
|
sys.stderr.write('done.\n')
|
|
# Clean up - no longer needed
|
|
os.unlink(distpath)
|
|
|
|
def install_setuptools(self, context):
|
|
"""
|
|
Install setuptools in the environment.
|
|
|
|
:param context: The information for the environment creation request
|
|
being processed.
|
|
"""
|
|
url = 'https://bitbucket.org/pypa/setuptools/downloads/ez_setup.py'
|
|
self.install_script(context, 'setuptools', url)
|
|
# clear up the setuptools archive which gets downloaded
|
|
pred = lambda o: o.startswith('setuptools-') and o.endswith('.tar.gz')
|
|
files = filter(pred, os.listdir(context.bin_path))
|
|
for f in files:
|
|
f = os.path.join(context.bin_path, f)
|
|
os.unlink(f)
|
|
|
|
def install_pip(self, context):
|
|
"""
|
|
Install pip in the environment.
|
|
|
|
:param context: The information for the environment creation request
|
|
being processed.
|
|
"""
|
|
url = 'https://raw.github.com/pypa/pip/master/contrib/get-pip.py'
|
|
self.install_script(context, 'pip', url)
|
|
|
|
def main(args=None):
|
|
compatible = True
|
|
if sys.version_info < (3, 3):
|
|
compatible = False
|
|
elif not hasattr(sys, 'base_prefix'):
|
|
compatible = False
|
|
if not compatible:
|
|
raise ValueError('This script is only for use with '
|
|
'Python 3.3 or later')
|
|
else:
|
|
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 to create the environment in.')
|
|
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 '
|
|
'environment directory if it '
|
|
'already exists, before '
|
|
'environment creation.')
|
|
parser.add_argument('--upgrade', default=False, action='store_true',
|
|
dest='upgrade', help='Upgrade the 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/4673395>`_.
|