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

Example: interactive shell

$ cd /path/to/myProject
$ vien create
$ vien shell

Example: running commands

$ cd /path/to/myProject
$ vien create
$ vien run pip install --upgrade pip
$ vien run pip install requests lxml
$ vien call main.py

Commands

create

vien create сreates a virtual environment that will correspond the current
working directory. The working directory in this case is assumed to be
your project directory. Subsequent calls to other vien commands in the
same directory will use the same 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, you can provide an argument to point
to the proper interpreter.

$ vien create /usr/local/opt/[email protected]/bin/python3

In many cases, a shorter command will also work. If the needed interpreter can
be executed in the shell as python3.8, you can try

$ vien create python3.8

shell

vien shell starts interactive bash session in the virtual environment.

$ 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

vien run COMMAND runs any shell command in the virtual environment.

$ cd /path/to/myProject
$ vien run python3 use_requests.py arg1 arg2  # runs script 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

call

vien call PYFILE executes a .py script in the virtual environment.

$ cd /path/to/myProject
$ vien call main.py

The optional -p parameter allows you to specify the project directory
relative to the parent directory of the file being run.

$ cd any/where  # working dir is irrelevant

# absolute (using venv for /abc/myProject):
$ vien call -p /abc/myProject /abc/myProject/main.py

# relative (using venv for /abc/myProject):
$ vien call -p . /abc/myProject/main.py

# error (there is no venv for any/where)
$ vien call /abc/myProject/main.py

This parameter makes things like shebang possible.

delete

vien delete deletes the virtual environment.

$ cd /path/to/myProject
$ vien delete 

recreate

vien recreate old and creates new virtual environment.

If you decided to start from scratch:

$ cd /path/to/myProject
$ vien recreate 

If you decided to change the Python version:

$ cd /path/to/myProject
$ vien recreate /usr/local/opt/[email protected]/bin/python3

Virtual environments location

By default, vien places virtual environments in the $HOME/.vien directory.

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

Only the local name of the project directory matters.

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.

Shell prompt

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

[email protected]$ cd /abc/myProject
[email protected]$ vien shell

(myProject)[email protected]$ _

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)[email protected]$ _

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

On POSIX systems, you can make a .py file executable, with vien executing it
inside a virtual environment.

Insert the shebang line to the top of the file you want to run. The value of the
shebang depends on the location of the file relative to the project directory.

File Shebang line
myProject/runme.py #!/usr/bin/env vien call -p .
myProject/pkg/runme.py #!/usr/bin/env vien call -p ..
myProject/pkg/subpkg/runme.py #!/usr/bin/env vien call -p ../..

After inserting the shebang, make the file executable:

$ chmod +x runme.py  

Now you can run the runme.py directly from command line. This will use the
virtual environment associated with the myProject. The working directory can
be anything.

# runs the runme.py in virtual environment for myProject

$ cd anywhere/somewhere
$ /abc/myProject/pkg/main.py   

GitHub

https://github.com/rtmigo/vien_py