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.
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
$ cd /path/to/myProject
$ vien create
$ vien shell
$ cd /path/to/myProject
$ vien create
$ vien run pip install --upgrade pip
$ vien run pip install requests lxml
$ vien call main.py
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/python@3.8/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
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.
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
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.
vien delete
deletes the virtual environment.
$ cd /path/to/myProject
$ vien delete
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/python@3.10/bin/python3
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.
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.
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