seven62/pyenv-notes.md

## pyenv-notes.md

      
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              pyenv-notes.md
            
          
    PYENV


or how I learned to stop worrying and get things done with python

focusing on "weapon-system" macOS
cross-platform, including windows to some extent
https://github.com/pyenv/pyenv

problem:
dependency hell
python2 v python3
pip / pip3

goal:
install in user space
install multiple versions
choose what version you want to use
change between versions easily

why not use system python?
think of as belonging to the system     which python
also an old (now depricated?) version    python -V
requires sudo pip install (global), issue with multiple users
** some OS actually use packaged python, ex. yum. let's not break it
package manager?
typically install packages in global system space (not user)
things just get mucked up fast, soil your environment

solution: pyenv (gh image)

installation overview
deps:
$ brew install openssl readline sqlite3 xz zlib
# mojave+ $ sudo installer -pkg /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg -target /
$ curl https://pyenv.run | bash

  WARNING: seems you still have not added 'pyenv' to the load path.

  # Load pyenv automatically by adding
  # the following to ~/.bashrc:

  export PATH="$HOME/.pyenv/bin:$PATH"
  eval "$(pyenv init -)"
  eval "$(pyenv virtualenv-init -)"

  (restart terminal)


where it's installed:
$ ls ~/.pyenv/versions/
$ pyenv uninstall 2.7.15 OR $ rm -rf ~/.pyenv/versions/2.7.15

installation lab

using pyenv overview

pyenv usage lab
getting info
$ pyenv # list available cli options
$ pyenv install --list (grep!) # list packages / versions available
$ pyenv install -v 3.7.2 # install
$ pyenv versions    # list installed versions
$ pyenv version     # list active version
$ pyenv global 2.7.15 # set new global version

scope
global  # use a particular Python version "by default"
local   # used to set an application-specific Python version
$ pyenv local x.x.x
creates a .python-version file in your current directory
shell   # set a shell-specific Python version
$ pyenv shell x.x.x

virtual environments
create an isolated environment for Python projects.
each project can have its own dependencies, regardless of dependencies
this may fit your existing workflow...

process overview:
$ pyenv virtualenv <python_version> <environment_name>
$ pyenv virtualenv 3.6.8 myproject
$ pyenv local myproject   # activate the new env