mkenv 3.4.0

A simpler tool for creating venvs in a central location

mkenv is a tool for configuring, in a single file, a set of virtualenvs, which packages to install into each, and any binaries to make globally available from within.

Installation

The usual:

$ pip install mkenv

Usage

The best way to use mkenv is by creating a file named ~/.local/share/virtualenvs/virtualenvs.toml. Here’s an example of what goes in it:

[virtualenv.development]
install = [
    "pudb",
    "twisted",
]
link = ["trial"]

[virtualenv.app]
install = ["$DEVELOPMENT/myapp"]

After creating the above, running convergeenvs will create 2 virtualenvs, one called “development” with pudb and twisted installed into it and trial linked from within it onto your PATH, and a second called “app” installing the corresponding directory.

That’s about all you need to know. If you insist on reading further though, mkenv has an older, not-very-recommended mutable interface which allows you to create virtualenvs in a central location without tracking them in a config file (or converging them). For that, usage is similar to mkvirtualenv, although mkenv passes arguments directly through to virtualenv:

$ mkenv nameofvenv -- -p pypy

will create a virtual environment in an appropriate platform-specific data directory, or in the directory specified by WORKON_HOME for compatibility with virtualenvwrapper.

Single-Purpose Virtualenvs

A common use case for virtualenvs is for single-purpose installations, e.g.:

“I want to install fabric and give it its own virtualenv so that its dependencies can be independently upgraded, all while still being able to use the fab binary globally”.

mkenv supports a --link option for this use case:

$ mkenv -i fabric --link fab

will create a virtualenv for fabric (in the same normal location), but will symlink the fab binary from within the virtualenv into your ~/.local/bin directory.

(You may have heard of pipsi which is a similar tool for this use case, but with less customization than I would have liked.)

Temporary Virtualenvs

I also find mktmpenv useful for quick testing. To support its use case, mkenv currently supports a different but similar style of temporary virtualenv.

Invoking:

$ venv=$(mkenv -t)

in your shell will create (or re-create) a global temporary virtualenv, and print its bin/ subdirectory (which in this case will be then stored in the venv variable). It can subsequently be used by, e.g.:

$ $venv/python

or:

$ $venv/pip ...

et cetera.

You may prefer using:

$ cd $(mkenv -t)

as your temporary venv workflow if you’re into that sort of thing instead.

The global virtualenv is cleared each time you invoke mkenv -t. Unless you care, unlike virtualenvwrapper’s mktmpenv, there’s no need to care about cleaning it up, whenever it matters for the next time, it will be cleared and overwritten.

mkenv may support the more similar “traditional” one-use virtualenv in the future, but given that it does not activate virtualenvs by default (see below), the current recommendation for this use case would be to simply use the virtualenv binary directly.

The 5 Minute Tutorial

Besides the mkenv for named-virtualenv creation and mkenv -t for temporary-virtualenv creation described above:

$ findenv name foo

will output (to standard output) the path to a virtualenv with the given name (see also --existing-only), and:

$ rmenv foo

will remove it.

There are a number of other slight variants, see the --help information for each of the three binaries.

Real documentation to come (I hope)

Why don’t I use virtualenvwrapper?

virtualenvwrapper is great! I’ve used it for a few years. But I’ve slowly settled on a much smaller subset of its functionality that I like to use. Specifically:

• I don’t like activating virtualenvs.

  virtualenvs are magical and hacky enough on their own, and piling activation on top just makes things even more messy for me, especially when moving around between different projects in a shell. Some people use cd tricks to solve this, but I just want simplicity.

• I don’t need project support.

  I’ve never attached a project to a virtualenv. I just use a naming convention, naming the virtualenv with the name of the repo (with simple coersion), and then using dynamic directory expansion in my shell to handle association.

Basically, I just want a thing that is managing a central repository of virtualenvs for me. So that’s what mkenv does.