Pyenv Notes

Functions and Reasons for Using pyenv

pyenv is a tool used to install various versions of Python on a system,

and to conveniently switch between Python versions.

When you need to develop or maintain projects that require different Python versions simultaneously,

you will need to use pyenv to help switch Python versions.

New Python versions usually include syntax updates or new features.

For example, Python’s async / await feature appeared only in Python 3.5 and later.

Projects developed with Python versions below 3.5 cannot use it.

Another example is having projects that use both Python 2 and Python 3.

Since Python 2 and Python 3 are syntactically incompatible,

it is necessary to install both Python 2 and Python 3 on the system.

In such cases, pyenv can be used to conveniently switch Python versions.

Installation and Initialization

Installation

brew install pyenv

After installation, run initialization

pyenv init

Then, follow the instructions to paste the displayed code into ~/.zshrc or ~/.bash_profile

Common Commands

• List available Python versions for installation

pyenv install --list

This will show:

Available versions:
  2.1.3
  2.2.3
  2.3.7
  2.4.0
	...
  3.9.6
  3.9.7
  3.10.0
  3.10-dev
  3.11.0a1
	...

• Install a specific Python version

pyenv install 3.10.0

• Observe which Python versions have been installed

pyenv versions

This will show:

* system (set by ......./.pyenv/version)
  3.10.0

This indicates that the system’s default version and the recently installed 3.10.0 are available,

but the currently used Python version is the system’s default.

• Switch the system-wide Python version

pyenv global 3.10.0

Running pyenv versions anywhere in the system will show that the currently used Python version is 3.10.0.

• Switch the Python version only for the current directory

pyenv local 3.7.12

In the current directory, pyenv versions will show that version 3.7.12 is being used.

However, in other directories,

if a version was previously set using pyenv global (e.g., 3.10.0),

then pyenv versions will show the version set by pyenv global (3.10.0).

If pyenv global was not run to set a version, pyenv versions will show the system’s default version.

• Uninstall a specific Python version

pyenv uninstall 3.7.12

Reference

pyenv Github