mise-migrate-from-pyenv

Migrating from pyenv to mise

pyenv is the long-standing Python version manager. mise replaces it with the same underlying python-build backend (same compile path, same options) plus support for pre-built binaries and integration with every other language you use. Migration is usually painless.

What mise gives you over pyenv

• Same python-build backend → same versions available, same build flags, same compile reliability.
• Optional pre-built binaries via MISE_PYTHON_COMPILE=0 — 10x faster installs.
• One version manager for every language, not just Python.
• Per-project [env] and [tasks] — pyenv doesn't do either.
• Auto-activated venvs via _.python.venv.
• Faster shell startup — mise is written in Rust, pyenv is shell functions.

The migration plan

1. Inventory pyenv state.
2. Create mise.toml per project (or enable idiomatic reader).
3. Swap shell rc.
4. Verify.
5. Uninstall pyenv (and pyenv-virtualenv if present).

Step 1 — inventory

pyenv versions                  # installed Python versions
pyenv version                   # current version
pyenv global                    # global default
pyenv local                     # in-project local pin (reads .python-version)
grep -r pyenv ~/.zshrc ~/.bashrc ~/.bash_profile 2>/dev/null
ls .python-version 2>/dev/null  # per-project version file

Also check for pyenv-virtualenv:

pyenv virtualenvs
cat .python-version   # may contain a virtualenv name like "myproject-3.12.7"

pyenv-virtualenv is a plugin that lets .python-version contain a virtualenv name instead of a bare version. If your .python-version has something like myproject-3.12.7, you'll need to handle that separately (see "pyenv-virtualenv migration" below).

Step 2 — mise.toml per project

For a plain .python-version containing 3.12.7:

# mise.toml
[tools]
python = "3.12.7"

Or enable the idiomatic reader and let mise read .python-version directly:

# mise.toml or ~/.config/mise/config.toml
[settings]
idiomatic_version_file_enable_tools = ["python"]

For pre-built binaries (strongly recommended — much faster):

[env]
MISE_PYTHON_COMPILE = "0"

Or set it globally in your shell rc.

Global default

# ~/.config/mise/config.toml
[tools]
python = "3.12"

[env]
MISE_PYTHON_COMPILE = "0"

Step 3 — swap shell rc

Remove pyenv's init:

# ~/.zshrc — DELETE
export PYENV_ROOT="$HOME/.pyenv"
[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init - zsh)"
eval "$(pyenv virtualenv-init -)"   # if you had pyenv-virtualenv

Add mise:

eval "$(mise activate zsh)"

Restart shell.

Step 4 — verify

which python            # should be under ~/.local/share/mise/
python --version        # matches mise.toml
cd <project>
python --version        # matches the project's pin

If which python shows a pyenv path, the old PATH is sticky. Check for leftover pyenv lines, then open a fresh terminal.

pyenv-virtualenv migration

pyenv-virtualenv stores .python-version with a venv name (e.g. myproject-3.12.7) and creates a venv under ~/.pyenv/versions/myproject-3.12.7/. mise doesn't have a direct equivalent, but _.python.venv is the idiomatic replacement:

Before (pyenv-virtualenv)

.python-version contains: myproject-3.12.7
Venv lives in:            ~/.pyenv/versions/myproject-3.12.7/

After (mise)

# mise.toml
[tools]
python = "3.12.7"

[env]
_.python.venv = { path = ".venv", create = true }

Venv lives in: .venv/ (in the project dir, gitignored)

.venv/ is in-project instead of centrally located. Pro: easier to blow away and recreate, no centralized cache to prune. Con: every project has its own full venv (but the Python interpreter itself is shared via mise's install dir, so this is less disk-heavy than it sounds).

If you want to keep a pyenv-virtualenv-style centralized layout:

[env]
_.python.venv = { path = "~/.cache/venvs/{{config_root | basename}}", create = true }

Not the idiomatic pattern, but possible.

Step 5 — uninstall pyenv

rm -rf ~/.pyenv
# If installed via Homebrew:
brew uninstall pyenv pyenv-virtualenv

Restart the shell. Verify which pyenv reports not found.

Common issues

"SSL module not available" after migrating

You migrated to mise's compiled Python and the host is missing libssl-dev (or the equivalent). See mise-lang-python-overview → "Build dependencies". Or switch to pre-built: MISE_PYTHON_COMPILE=0 mise install python@<version>.

pip install fails with "externally-managed-environment"

You're pip install-ing into the mise-installed Python's system site (PEP 668 error). Always use a venv:

python -m venv .venv
source .venv/bin/activate
pip install <pkg>

Or, better, use uv or poetry + _.python.venv to manage this for you. See mise-lang-python-packages.

python --version shows a different version than mise current python

Shim cache staleness. Run mise reshim and reopen the shell.

IDE still finds the pyenv Python

Point the IDE at the mise-installed interpreter explicitly:

~/.local/share/mise/installs/python/3.12.7/bin/python

Or the shim:

~/.local/share/mise/shims/python

The shim re-resolves on each invocation, so it always picks the project-correct version.

Multiple Python versions (pyenv users often have many)

[tools]
python = "3.12 3.11 3.10"   # three versions, 3.12 is default

mise installs and makes all three available. python3.11 --version works; bare python resolves to the first.

Global tools (pipx / pip --user equivalents)

If you were using pip install --user black flake8 ruff or pipx, move to mise's pipx: backend:

# ~/.config/mise/config.toml
[tools]
python = "3.12"
"pipx:ruff" = "latest"
"pipx:black" = "latest"
"pipx:httpie" = "latest"

Version-pinned, managed, survives Python version upgrades (pipx detects and rebuilds).

Rollback

Reinstall pyenv if needed (your .python-version files are untouched):

curl -L https://github.com/pyenv/pyenv-installer/raw/master/bin/pyenv-installer | bash

Remove mise activation from shell rc. Restart shell.

See also

• mise-lang-python-overview — Python version resolution.
• mise-lang-python-packages — uv / poetry / pipx decision.
• mise-env-directives — _.python.venv auto-activation.
• mise-migrate-from-asdf — general migration shape.
• mise docs: mise.jdx.dev/faq.html#migrating-from-pyenv.
• python-build-standalone: github.com/astral-sh/python-build-standalone.