Atom

1. Install Atom and the ide-python package:

   brew cask install atom
   apm install atom-ide-ui
   apm install ide-python 

2. Create a Python virtualenv and install pyls-black along with its dependencies:

   # Create a directory to keep your virtualenvs in
   mkdir -p ~/.virtualenvs
   
   # Create a new virtualenv
   python3 -m venv ~/.virtualenvs/ide-python
   
   # Install pyls-black in the newly created virtualenv
   ~/.virtualenvs/ide-python/bin/python3 -m pip install pyls-black

   Note: this will create a virtualenv in ~/.virtualenvs/ide-python but the exact location is up to you!

3. Set the Python path in the ide-python:

   Atom → Preferences → Packages → ide-python → Under Settings → Python Executable

   It should be set to the full path to the Python executable created in the previous step: /Users/rupert/.virtualenvs/ide-python/bin/python3 (replace /Users/rupert with the path to your home folder - ~ is not expanded).

   An alternative is to update your Atom config file directly:

   # config.cson
   
   "*":
     "ide-python":
       python: "/Users/rupert/.virtualenvs/ide-python/bin/python3"

Format on Save

Atom → Preferences → Packages → atom-ide-ui → Under Code Formatting → Format on Save

Alternatively you can update your Atom config file directly:

# config.cson

"*":
  "atom-ide-ui":
    "atom-ide-code-format":
      formatOnSave: true