venv
--- Creation of virtual environments¶
Ajouté dans la version 3.3.
Code source : Lib/venv/
The venv
module supports creating lightweight "virtual environments",
each with their own independent set of Python packages installed in
their site
directories.
A virtual environment is created on top of an existing
Python installation, known as the virtual environment's "base" Python, and may
optionally be isolated from the packages in the base environment,
so only those explicitly installed in the virtual environment are available.
When used from within a virtual environment, common installation tools such as pip will install Python packages into a virtual environment without needing to be told to do so explicitly.
A virtual environment is (amongst other things):
Used to contain a specific Python interpreter and software libraries and binaries which are needed to support a project (library or application). These 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 named
.venv
orvenv
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.
Not considered as movable or copyable -- you just recreate the same environment in the target location.
See PEP 405 for more background on Python virtual environments.
Availability: not Emscripten, not WASI.
This module does not work or is not available on WebAssembly platforms
wasm32-emscripten
and wasm32-wasi
. See
Plateformes WebAssembly for more information.
Création d'environnements virtuels¶
Virtual environments are created by executing the venv
module:
python -m venv /path/to/new/virtual/environment
This creates the target directory (including parent directories as needed)
and places a pyvenv.cfg
file in it with a home
key
pointing to the Python installation from which the command was run.
It also creates a bin
(or 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 lib/pythonX.Y/site-packages
subdirectory
(on Windows, this is Libsite-packages
).
If an existing directory is specified, it will be re-used.
Modifié dans la version 3.5: L'utilisation de venv
est maintenant recommandée pour créer vos environnements virtuels.
Deprecated since version 3.6, removed in version 3.8: 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.
On Windows, invoke the venv
command as follows:
PS> python -m venv C:\path\to\new\virtual\environment
La commande, si lancée avec -h
, montrera les options disponibles :
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.
Modifié dans la version 3.4: Installs pip by default, added the --without-pip
and --copies
options.
Modifié dans la version 3.4: Dans les versions précédentes, si le dossier de destination existait déjà, une erreur était levée, sauf si l'option --clear
ou --upgrade
était incluse.
Modifié dans la version 3.9: Add --upgrade-deps
option to upgrade pip + setuptools to the latest on PyPI.
Modifié dans la version 3.12: setuptools
is no longer a core venv dependency.
Note
Bien que les liens symboliques soient pris en charge sous Windows, ils ne sont pas recommandés. Il est particulièrement à noter que le double-clic sur python.exe
dans l'Explorateur de fichiers suivra le lien symbolique et ignorera l'environnement virtuel.
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:
PS C:\> Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
See About Execution Policies for more information.
The created 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.
Sauf si l'option --without-pip
est incluse, ensurepip
sera invoqué pour amorcer pip
dans l'environnement virtuel.
Plusieurs chemins peuvent être donnés à venv
, et dans ce cas un environnement virtuel sera créé, en fonction des options incluses, à chaque chemin donné.
How venvs work¶
When a Python interpreter is running from a virtual environment,
sys.prefix
and sys.exec_prefix
point to the directories of the virtual environment,
whereas sys.base_prefix
and sys.base_exec_prefix
point to those of the base Python used to create the environment.
It is sufficient to check
sys.prefix != sys.base_prefix
to determine if the current interpreter is
running from a virtual environment.
A virtual environment may be "activated" using a script in its binary directory
(bin
on POSIX; Scripts
on Windows).
This will prepend that directory to your PATH
, so that running
python will invoke the environment's Python interpreter
and you can run installed scripts without having to use their full path.
The invocation of the activation script is platform-specific
(<venv>
must be replaced by the path to the directory
containing the virtual environment):
Plateforme |
Invite de commande |
Commande pour activer l'environnement virtuel |
---|---|---|
POSIX |
bash/zsh |
|
fish |
|
|
csh/tcsh |
|
|
pwsh |
|
|
Windows |
cmd.exe |
|
PowerShell |
|
Ajouté dans la version 3.4: fish and csh activation scripts.
Ajouté dans la version 3.8: Scripts d'activation PowerShell installés sous POSIX pour le support de PowerShell Core.
You don't specifically need to activate a virtual environment, as you can just specify the full path to that environment's Python interpreter when invoking Python. Furthermore, all scripts installed in the environment 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,
#!/<path-to-venv>/bin/python
.
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 Lanceur Python pour Windows installed. Thus, double-clicking an installed
script in a Windows Explorer window should run it with the correct interpreter
without the environment needing to be activated or on the PATH
.
When a virtual environment has been activated, the VIRTUAL_ENV
environment variable is set to the path of the environment.
Since explicitly activating a virtual environment is not required to use it,
VIRTUAL_ENV
cannot be relied upon to determine
whether a virtual environment is being used.
Avertissement
Because scripts installed in environments should not expect the
environment to be activated, their shebang lines contain the absolute paths
to their environment's interpreters. Because of this, environments are
inherently non-portable, in the general case. You should always have a
simple means of recreating an environment (for example, if you have a
requirements file requirements.txt
, you can invoke pip install -r
requirements.txt
using the environment's pip
to install all of the
packages needed by the environment). If for any reason you need to move the
environment to a new location, you should recreate it at the desired
location and delete the one at the old location. If you move an environment
because you moved a parent directory of it, you should recreate the
environment in its new location. Otherwise, software installed into the
environment may not work as expected.
You can deactivate a virtual environment by typing deactivate
in your shell.
The exact mechanism is platform-specific and is an internal implementation
detail (typically, a script or shell function will be used).
API¶
La méthode haut niveau décrite au dessus utilise une API simple qui permet à des créateurs d'environnements virtuels externes de personnaliser la création d'environnements virtuels basés sur leurs besoins, la classe EnvBuilder
.
- class venv.EnvBuilder(system_site_packages=False, clear=False, symlinks=False, upgrade=False, with_pip=False, prompt=None, upgrade_deps=False)¶
La classe
EnvBuilder
accepte les arguments suivants lors de l'instanciation :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 rather than copying.
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
).with_pip -- a boolean value which, if true, ensures pip is installed in the virtual environment. This uses
ensurepip
with the--default-pip
option.prompt -- a string to be used after virtual environment is activated (defaults to
None
which means directory name of the environment would be used). If the special string"."
is provided, the basename of the current directory is used as the prompt.upgrade_deps -- Update the base venv modules to the latest on PyPI
Modifié dans la version 3.4: Ajout du paramètre
with_pip
Modifié dans la version 3.6: Ajout du paramètre
prompt
Modifié dans la version 3.9: Added the
upgrade_deps
parameterEnvBuilder
may be used as a base class.- create(env_dir)¶
Crée un environnement virtuel en spécifiant le chemin cible (absolu ou relatif par rapport au dossier courant) qui contiendra l'environnement virtuel. La méthode
create
crée l'environnement dans le dossier spécifié ou lève une exception appropriée.La méthode
create
de la classeEnvBuilder
illustre les points d'entrées disponibles pour la personnalisation de sous-classes :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)
Chacune des méthodes
ensure_directories()
,create_configuration()
,setup_python()
,setup_scripts()
etpost_setup()
peuvent être écrasés.
- ensure_directories(env_dir)¶
Creates the environment directory and all necessary subdirectories that don't already exist, and returns a context object. This context object is just a holder for attributes (such as paths) for use by the other methods. If the
EnvBuilder
is created with the argclear=True
, contents of the environment directory will be cleared and then all necessary subdirectories will be recreated.The returned context object is a
types.SimpleNamespace
with the following attributes:env_dir
- The location of the virtual environment. Used for__VENV_DIR__
in activation scripts (seeinstall_scripts()
).env_name
- The name of the virtual environment. Used for__VENV_NAME__
in activation scripts (seeinstall_scripts()
).prompt
- The prompt to be used by the activation scripts. Used for__VENV_PROMPT__
in activation scripts (seeinstall_scripts()
).executable
- The underlying Python executable used by the virtual environment. This takes into account the case where a virtual environment is created from another virtual environment.inc_path
- The include path for the virtual environment.lib_path
- The purelib path for the virtual environment.bin_path
- The script path for the virtual environment.bin_name
- The name of the script path relative to the virtual environment location. Used for__VENV_BIN_NAME__
in activation scripts (seeinstall_scripts()
).env_exe
- The name of the Python interpreter in the virtual environment. Used for__VENV_PYTHON__
in activation scripts (seeinstall_scripts()
).env_exec_cmd
- The name of the Python interpreter, taking into account filesystem redirections. This can be used to run Python in the virtual environment.
Modifié dans la version 3.11: The venv sysconfig installation scheme is used to construct the paths of the created directories.
Modifié dans la version 3.12: The attribute
lib_path
was added to the context, and the context object was documented.
- create_configuration(context)¶
Crée le fichier de configuration
pyvenv.cfg
dans l'environnement.
- setup_python(context)¶
Crée une copie ou un lien symbolique vers l'exécutable Python dans l'environnement. Sur les systèmes POSIX, si un exécutable spécifique
python3.x
a été utilisé, des liens symboliques verspython
etpython3
seront créés pointant vers cet exécutable, sauf si des fichiers avec ces noms existent déjà.
- setup_scripts(context)¶
Installe les scripts d'activation appropriés à la plateforme dans l'environnement virtuel.
- upgrade_dependencies(context)¶
Upgrades the core venv dependency packages (currently pip) in the environment. This is done by shelling out to the
pip
executable in the environment.Ajouté dans la version 3.9.
Modifié dans la version 3.12: setuptools is no longer a core venv dependency.
- post_setup(context)¶
Une méthode qui n'est la que pour se faire surcharger dans des implémentation externes pour pré installer des paquets dans l'environnement virtuel ou pour exécuter des étapes post-création.
- install_scripts(context, path)¶
This method can be called from
setup_scripts()
orpost_setup()
in subclasses to assist in installing custom scripts into the virtual environment.path is the path to a directory that should contain subdirectories
common
,posix
,nt
; each containing scripts destined for thebin
directory in the environment. The contents ofcommon
and the directory corresponding toos.name
are copied after some text replacement of placeholders:__VENV_DIR__
est remplacé avec le chemin absolu du dossier de l'environnement.__VENV_NAME__
est remplacé avec le nom de l'environnement (le dernier segment du chemin vers le dossier de l'environnement).__VENV_PROMPT__
est remplacé par le prompt (nom de l'environnement entouré de parenthèses et avec un espace le suivant).__VENV_BIN_NAME__
est remplacé par le nom du dossier bin (soitbin
soitScripts
).__VENV_PYTHON__
est remplacé avec le chemin absolu de l’exécutable de l'environnement.
Les dossiers peuvent exister (pour quand un environnement existant est mis à jour).
Modifié dans la version 3.7.2: Windows utilise maintenant des scripts de redirection pour
python[w].exe
au lieu de copier les fichiers binaires. En 3.7.2 seulementsetup_python()
ne fait rien sauf s'il s'exécute à partir d'un build dans l'arborescence source.Modifié dans la version 3.7.3: Windows copie les scripts de redirection dans le cadre de
setup_python()
au lieu desetup_scripts()
. Ce n'était pas le cas en 3.7.2. Lorsque vous utilisez des liens symboliques, les exécutables originaux seront liés.
Il y a aussi une fonction pratique au niveau du module :
- venv.create(env_dir, system_site_packages=False, clear=False, symlinks=False, with_pip=False, prompt=None, upgrade_deps=False)¶
Crée une
EnvBuilder
avec les arguments donnés, et appelle sa méthodecreate()
avec l'argument env_dir.Ajouté dans la version 3.3.
Modifié dans la version 3.4: Added the with_pip parameter
Modifié dans la version 3.6: Added the prompt parameter
Modifié dans la version 3.9: Added the upgrade_deps parameter
Un exemple d'extension de EnvBuilder
¶
Le script qui suis montre comment étendre EnvBuilder
en implémentant une sous-classe qui installe setuptools et pip dans un environnement créé :
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 virtual environment.
:param nodist: If true, setuptools and pip are not installed into the
created virtual environment.
:param nopip: If true, pip is not installed into the created
virtual 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
virtual environment being created.
:param context: The information for the virtual 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 virtual environment'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 virtual environment
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 virtual environment.
:param context: The information for the virtual environment
creation request being processed.
"""
url = "https://bootstrap.pypa.io/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 virtual environment.
:param context: The information for the virtual environment
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)
Ce script est aussi disponible au téléchargement en ligne.