Source code:Lib/venv/
The
venv module provides support for creating lightweight “virtualenvironments” with their own site directories, optionally isolated from systemsite directories. Each virtual environment has its own Python binary (whichmatches the version of the binary that was used to create this environment) andcan have its own independent set of installed Python packages in its sitedirectories.
See PEP 405 for more information about Python virtual environments.
Mar 12, 2020 After creating the bootable installer, follow these steps to use it. Plug the bootable installer into a compatible Mac.; Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it. Mar 29, 2019 How to Open Exe Files on Mac. This wikiHow teaches you how to run Windows' executable (EXE) files on a Mac. To do so, you can either install WINE, which is free software, or install Windows 8 or 10 using your Mac's Boot Camp feature. Apr 11, 2017 This module loads environment variables from a.env file that you create and adds them to the process.env object that is made available to the application. Using dotenv It’s pretty simple to use. Creating.env file in Windows. Windows do not allow you to create a.env file directly from the windows explorer since it will not allow file names starting with a dot. However, you will be able to create it from VSCode easily. First, open the project folder in VSCode using the menu option File Open Folder.Ctrl+K Ctrl+O as shown in the following screenshot. Dec 29, 2019 Find the correct file name. Your file name must include the extension at the end of its name. If the extension is hidden, use any of these methods to find it: Select the file in Finder. Press ⌘ Command + I. In the Info window, look for 'file name & extension' to see the whole name. Or switch directories to the folder that contains the file.
See also
Creating virtual environments¶
Creation of virtual environments is done by executing thecommand
venv :
Running this command creates the target directory (creating any parentdirectories that don’t exist already) and places a
pyvenv.cfg file in itwith a home key pointing to the Python installation from which the commandwas run (a common name for the target directory is .venv ). It also createsa bin (or Scripts on Windows) subdirectory containing a copy/symlinkof the Python binary/binaries (as appropriate for the platform or argumentsused at environment creation time). It also creates an (initially empty)lib/pythonX.Y/site-packages subdirectory (on Windows, this isLibsite-packages ). If an existing directory is specified, it will bere-used.
Deprecated since version 3.6:
pyvenv was the recommended tool for creating virtual environments forPython 3.3 and 3.4, and is deprecated in Python 3.6.
Changed in version 3.5: The use of
venv is now recommended for creating virtual environments.
On Windows, invoke the
venv command as follows:
Alternatively, if you configured the
PATH and PATHEXT variables foryour Python installation:
The command, if run with
-h , will show the available options:
Changed in version 3.4: Installs pip by default, added the
--without-pip and --copies options
Changed in version 3.4: In earlier versions, if the target directory already existed, an error wasraised, unless the
--clear or --upgrade option was provided.
Note
While symlinks are supported on Windows, they are not recommended. Ofparticular note is that double-clicking
python.exe in File Explorerwill 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 byissuing the following PowerShell command:
PS C:> Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
See About Execution Policiesfor more information.
Create .env File On Mac
The created
pyvenv.cfg file also includes theinclude-system-site-packages key, set to true if venv isrun with the --system-site-packages option, false otherwise.
Unless the
--without-pip option is given, ensurepip will beinvoked to bootstrap pip into the virtual environment.
Multiple paths can be given to
venv , in which case an identical virtualenvironment will be created, according to the given options, at each providedpath.
Once a virtual environment has been created, it can be “activated” using ascript in the virtual environment’s binary directory. The invocation of thescript is platform-specific (<venv> must be replaced by the path of thedirectory containing the virtual environment):
You don’t specifically need to activate an environment; activation justprepends the virtual environment’s binary directory to your path, so that“python” invokes the virtual environment’s Python interpreter and you can runinstalled scripts without having to use their full path. However, all scriptsinstalled in a virtual environment should be runnable without activating it,and run with the virtual environment’s Python automatically.
You can deactivate a virtual environment by typing “deactivate” in your shell.The exact mechanism is platform-specific and is an internal implementationdetail (typically a script or shell function will be used).
New in version 3.8: PowerShell activation scripts installed under POSIX for PowerShell Coresupport.
Note
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A virtual environment is a Python environment such that the Pythoninterpreter, libraries and scripts installed into it are isolated from thoseinstalled in other virtual environments, and (by default) any librariesinstalled in a “system” Python, i.e., one which is installed as part of youroperating system.
A virtual environment is a directory tree which contains Python executablefiles and other files which indicate that it is a virtual environment.
Common installation tools such as setuptools and pip work asexpected with virtual environments. In other words, when a virtualenvironment is active, they install Python packages into the virtualenvironment without needing to be told to do so explicitly.
When a virtual environment is active (i.e., the virtual environment’s Pythoninterpreter is running), the attributes
sys.prefix andsys.exec_prefix point to the base directory of the virtualenvironment, whereas sys.base_prefix andsys.base_exec_prefix point to the non-virtual environment Pythoninstallation which was used to create the virtual environment. If a virtualenvironment is not active, then sys.prefix is the same assys.base_prefix and sys.exec_prefix is the same assys.base_exec_prefix (they all point to a non-virtual environmentPython installation).
When a virtual environment is active, any options that change theinstallation path will be ignored from all
distutils configurationfiles to prevent projects being inadvertently installed outside of thevirtual environment.
When working in a command shell, users can make a virtual environment activeby running an
activate script in the virtual environment’s executablesdirectory (the precise filename and command to use the file isshell-dependent), which prepends the virtual environment’s directory forexecutables to the PATH environment variable for the running shell. Thereshould be no need in other circumstances to activate a virtualenvironment; scripts installed into virtual environments have a “shebang”line which points to the virtual environment’s Python interpreter. This meansthat the script will run with that interpreter regardless of the value ofPATH . On Windows, “shebang” line processing is supported if you have thePython Launcher for Windows installed (this was added to Python in 3.3 - seePEP 397 for more details). Thus, double-clicking an installed script in aWindows Explorer window should run the script with the correct interpreterwithout there needing to be any reference to its virtual environment inPATH .
API¶
The high-level method described above makes use of a simple API which providesmechanisms for third-party virtual environment creators to customize environmentcreation according to their needs, the
EnvBuilder class.
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