Python Version Management & Virtual Environments

Python Version Management - pyenv

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pyenv lets you easily switch between multiple versions of Python. It’s simple, unobtrusive, and follows the UNIX tradition of single-purpose tools that do one thing well.

What pyenv does…

Lets you change the global Python version on a per-user basis (pyenv global).
Provides support for per-project Python versions (pyenv local).
Allows you to override the Python version with an environment variable (pyenv shell).
Searches for commands from multiple versions of Python at a time. This may be helpful to test across Python versions with tox .

In contrast with pythonbrew (no longer under active development) and pythonz, pyenv does not…

Depend on Python itself. pyenv was made from pure shell scripts. There is no bootstrap problem of Python.
Need to be loaded into your shell. Instead, pyenv’s shim approach works by adding a directory to your PATH.
Manage virtualenv. Of course, you can create virtualenv yourself, or pyenv-virtualenv to automate the process.

Installation

1	brew install pyenv

Then follow the rest of the post-installation steps, starting with Set up your shell environment for Pyenv.

Add the following to .zshrc:

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export PYENV_ROOT="$HOME/.pyenv"
eval "$(pyenv init -)"
# eval "$(pyenv init --path)"

pyenv needs to be upgraded to install new Python versions:

1 2	brew upgrade pyenv pyenv install --list

Usage

If BUILD FAILED on Mac OS when pyenv install x.y.z:

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sudo rm -rf /Library/Developer/CommandLineTools
xcode-select --install
pyenv install x.y.z

To select a pyenv-installed Python as the version to use, run one of the following commands:

pyenv shell <version> – select just for current shell session（在环境变量 PYENV_VERSION 中设置指定的 version）
pyenv local <version> – automatically select whenever you are in the current directory (or its subdirectories)（在当前目录创建一个 .python-version 文件，记录指定的 version）
pyenv global <version> – select globally for your user account（在 $PYENV_ROOT 目录中创建一个 version 文件，记录指定的 version）

Plugins

Plugins · pyenv/pyenv Wiki

除了 pyenv-virtualenv，没什么特别需要的。

Virtual Environments Management - pyenv-virtualenv

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pyenv-virtualenv is a pyenv plugin that provides features to manage virtualenvs and conda environments for Python on UNIX-like systems.

Note

pyenv-veirtualenv is preferred rather than pyenv-virtualenvwrapper

# 2022-08-04 10:37 The last release (v1.1.5) was on Feb 14, 2019
brew install --HEAD pyenv-virtualenv
# Or simply clone plugin code into pyenv plugins folder:
git clone https://github.com/pyenv/pyenv-virtualenv.git $(pyenv root)/plugins/pyenv-virtualenv

Zsh has a pyenv plugin, which also loads pyenv-virtualenv if exists.

# Create virtualenv
pyenv virtualenv <name>
pyenv virtualenv 2.7.10 <name>

# Activate virtualenv
pyenv activate <name>
pyenv deactivate

# Delete existing virtualenv
pyenv uninstall <name>
# or
pyenv virtualenv-delete <name>

Virtualenvs can also be used by pyenv local, pyenv shell, or pyenv global if necessary.

Automatically Activate/Deactivate Virtualenvs

pyenv 虽然通过 pyenv local （即 .python-version 文件）也可以实现进入一个目录时自动切换到指定的 python 版本（支持多个版本、支持 virtualenv），但到目前（v2.3.2）仍然要求所指定的每一个版本必须存在，否则无法成功运行 python。虽然自动了，但过于强制。期望的是进入目录时，如果指定的版本（或 virtualenv）存在就自动切换，不存在就不切换。

pyenv-virtualenv 也说支持 auto activate，但也是基于 .python-version 文件，不知道跟 pyenv 自身的自动切换版本有什么区别（似乎是 pyenv-virtualenv 会额外 activate the virtualenv），但实际效果也是如果指定 virtualenv 不存在，就无法运行 python（这个是 pyenv 控制的）。

还没找到现成的工具或插件（for zsh or pyenv）。

考虑仿照 zsh virtualenvwrapper 插件里的逻辑，实现一个类似的基于 pyenv-virtualenv 的自动切换函数，可以不用额外的配置文件，自动找与目录同名的 virtualenv，如果有就 activate，没有就算了。