dansayo/Python Setup.md

## Python Setup.md

      
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              Python Setup.md
            
          
    Update:

overriding pyenv python versions, if you want to use a python version located on a different folder, i.e. /usr/local/bin/python3
on a new project, then:
mkdir <new_project>
cd <new_project>
<on new_project> mkdir venv
<on new_project> /usr/local/bin/python3 -m venv venv

Setting up a new Python project

This how-to uses the native venv. Goodbye to pipenv. pyenv still used.  Tested as my current workflow on Mac OS.  Linux should be happy, too.

A. Detailed steps


Choose your Python version


From available local versions -

~/dev $ pyenv versions

Or from the Internet, if no local version exists -

~/dev $ pyenv install -l
~/dev $ pyenv install 3.7.4

Set the version as system default

~/dev $ pyenv global 3.7.4

Set up the project folder

~/dev $ mkdir project-x
~/dev $ cd project-x
~/dev/project-x $ mkdir venv

Create the virtual environment

~/dev/project-x $ $(pyenv which python3) -m venv venv

Revert the system default Python version, if needed

~/dev/project-x $ pyenv global 3.6.8

Activate the virtual environment

~/dev/project-x $ source venv/bin/activate

Upgrade pip, if needed

(venv) ~/dev/project-x $ pip list
(venv) ~/dev/project-x $ pip install --upgrade pip


Work on the other Python packages, start-up VS Code, etc.


On VS Code, create a helloworld Python file to trigger VS Code asking for a Python interpreter; choose the appropriate venv and Python version. I also install pylint and black (via call to Format Document).  Sample pip list output of the base install -


(venv) ~/dev/project-x $ pip list
Package           Version
----------------- -------
appdirs           1.4.3
astroid           2.2.5
attrs             19.1.0
black             19.3b0
Click             7.0
isort             4.3.21
lazy-object-proxy 1.4.2
mccabe            0.6.1
pip               19.2.3
pylint            2.3.1
setuptools        40.6.2
six               1.12.0
toml              0.10.0
typed-ast         1.4.0
wrapt             1.11.2
(venv) ~/dev/project-x $
How to use linting:
Using pylint in VS-Code

Before closing a working day's session, deactivate the virtual

(venv) ~/dev/project-x $ deactivate
~/dev/project-x $

B. To recap


to activate

~/dev/project-x $ source venv/bin/activate

to deactivate

(venv) ~/dev/project-x $ deactivate

C. Transitioning from a pyenv virtualenv to the native venv

Be sure to pip freeze > requirements first.
pyenv uninstall <name of pyenv virtual env>
Proceed to create the venv virtualenv.
Restore Python package dependencies
pip install -r requirements.txt

D. Transitioning from a pipenv virtualenv to the native venv

Create a requirements from the pipenv lock output (copy-paste the output to requirements.txt) and remove the vm
pipenv lock -r
pipenv uninstall
pipenv --rm
Proceed to create the venv virtualenv.
Restore Python package dependencies
pip install -r requirements.txt
E. Updating pyenv

In Homebrew:
$ brew update && brew upgrade pyenv
Update pyenv:
$ pyenv update