vien 0.3.3

Command-line tool for managing Python virtual environments

vien

VIEN is a command-line tool for managing Python Virtual Environments.

It provides one-line shortcuts for:

• creating and deleting environments
• running commands inside environments
• switching between environments in bash shell

---

Switching between projects should be simple. Creating environments for the projects should be simple too.

Ideally it's a short command that I would type even half asleep.

Something like

$ vien create 
$ vien shell

Not like

$ python3 -m venv ./where/to/put/this/.venv
$ source /i/lost/that/.venv/bin/activate

Ready-made solutions did not help.

• pipenv kind of solved the problem, but brought new challenges unrelated to virtual environments
• virtualenvwrapper name is easier to copy-paste than to type. And its commands are too

So there is the vien. A tool for a half asleep developer.

Install

Get a working Python ≥3.7, pip3 and venv.

@ Ubuntu

$ sudo apt install -y python3 python3-pip python3-venv

@ macOS

$ brew install python3

Check it works

$ python3 --version             # python shows its version
$ python3 -m venv --help        # venv shows help message
$ pip3 install --upgrade pip    # pip upgrades itself

---

Then:

$ pip3 install vien

Make sure it installed:

$ vien      # shows help

Upgrade it later:

$ pip3 install vien --upgrade

Use

Create a virtual environment

$ cd /path/to/myProject
$ vien create 

By default vien will try to use python3 as the interpreter for the virtual environment.

If you have more than one Python version, provide one more argument.

Point to the proper interpreter the way you execute it.

If you execute scripts like that

$ python3.8 /path/to/script.py

Create virtual environment like that:

$ vien create python3.8

Or provide full path to the interpreter:

$ vien create /usr/local/opt/python@3.8/bin/python3

Dive into interactive bash

$ cd /path/to/myProject
$ vien shell

(myProject)$ _

Now you are inside the virtual environment.

(myProject)$ which python3             # now we are using separate copy of Python
(myProject)$ echo $PATH                # everything is slightly different

(myProject)$ pip3 install requests     # installs packages into virtual environment
(myProject)$ python3 use_requests.py   # runs inside the virtual environment

Get out of the virtual environment:

(myProject)$ exit

$ _

Now you're back.

Run a script inside the virtual environment

It is vien run <any bash command>

$ cd /path/to/myProject
$ vien run python3 use_requests.py arg1 arg2  # runs in virtual environment
$ vien run pip3 install requests              # installs packages into virtual environment

is an equivalent to

$ cd /path/to/myProject

$ source /path/to/the/venv/bin/activate
$ python3 use_requests.py arg1 arg2
$ /path/to/the/venv/bin/deactivate

$ source /path/to/the/venv/bin/activate
$ pip3 install requests
$ /path/to/the/venv/bin/deactivate

Where are those virtual environments

vien offers a simple rule of where to keep the environments.

project dir	virtual environment dir
/abc/thisProject	$HOME/.vien/thisProject_venv
/abc/otherProject	$HOME/.vien/otherProject_venv
/moved/to/otherProject	$HOME/.vien/otherProject_venv

So only the local name of the project directory matters. And all the virtual environments are in $HOME/.vien.

If you're not happy with the default, you can set the environment variable VIENDIR:

$ export VIENDIR="/x/y/z"

So for the project aaa the virtual environment will be located in /x/y/z/aaa_venv.

The _venv suffix tells the utility that this directory can be safely removed.

Other commands

Delete virtual environment

$ cd /path/to/myProject
$ vien delete 

Delete old and create new virtual environment

Useful, when you want to start from scratch.

$ cd /path/to/myProject
$ vien recreate 

Or upgrade it from an old Python to a new one:

$ cd /path/to/myProject
$ vien recreate /usr/local/opt/python@3.10/bin/python3

Shell prompt

By default the vien shell adds a prefix to the $PS1 bash prompt.

user@host$ cd /abc/myProject
user@host$ vien shell

(myProject)user@host$ _

So you can see, which virtual environment you're using.

If you customized your PS1, it may not work as expected.

personalized:prompt> cd /abc/myProject
personalized:prompt> vien shell

(myProject)user@host$ _

It can be fixed by providing PS1 variable to vien like that:

personalized:prompt> cd /abc/myProject
personalized:prompt> PS1=$PS1 vien shell

(myProject)personalized:prompt> _

To avoid doing this each time, export your PS1 to make it available for subprocesses.

Shebang

Add the following line to the top of main.py

#!/usr/bin/env vien run python

Make the main.py executable

$ chmod +x main.py  

Now you can run the main.py directly from command line. In will use the vien virtual environment associated with the parent directory of main.py.

$ /path/to/myProject/main.py

Of course, the virtual environment must be initialized if it is not already done

$ cd /abc/myProject
$ vien create
$ vien shell
$ pip install ...