pyem 0.3.0

Project-level Python virtual environment management tool.

PyEM manages multiple virtual environments local to projects. It provides shortcuts to create, remove, switch between, and run commands against virtual environments created against various Python interpreters.

In Action

Add a virtual environment:

$ pyem venv add python3.7  # Based on a command.

$ pyem venv add 3.6  # Based on interpreter found by the Python launcher.

$ pyem venv add /usr/local/bin/pypy3  # Based on an executable.

The second variant relies on the Python launcher to locate an interpreter. This tool should be installed by default if you use the officlal installer on Windows (and do not explicitly choose not to install it). For other platforms, Python launcher for UNIX by Brett Cannon can be used as an alternative.

List managed virtual environments:

$ pyem venv list
  Quintuplet
=============================================
  cpython-3.6-darwin-x86_64-f14a3513
  cpython-3.7-darwin-x86_64-dbe83ac5
* pypy-3.6-darwin-x86_64-dc1298a1

Set active virtual environment:

$ pyem venv set 3.7
Switched to cpython-3.7-darwin-x86_64-dbe83ac5

$ pyem venv set 3.6
Error: name '3.6' is ambiguous; choose from:
  cpython-3.6-darwin-x86_64-f14a3513
  pypy-3.6-darwin-x86_64-dc1298a1

$ pyem venv set cpython-3.6
Switched to cpython-3.6-darwin-x86_64-f14a3513

Run a command inside a virtual environment:

$ pyem poetry run python -c "import sys; print(sys.executable)"
/tmp/exampleproject/.venvs/bin/python

$ pyem --spec=pypy-3.6 pipenv run pypy3 -c "import sys; print(sys.executable)"
/tmp/exampleproject/.venvs/bin/pypy3

How does this work?

PyEM sets environment variables VIRTUAL_ENV and PATH, and hand off control to subprocess for the command specified. This is enough to trick a lot of Python project tools, including the Python launcher, Poetry, and Pipenv. Python interpreters with venv support (e.g. CPython 3.3 or later) should also integrate seamlessly.

Flit is more difficult to trick since it does not automatically inspect environment variables like other tools do. Use this workaround instead (requires the Python launcher):

$ pyem flit install --python=py