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Emacs Settings for Python

Stole Python package ideas from Gabriel Elanaro’s git project. The question is whether I use Rope or Jedi for auto-completion. Rope, while claiming more features, seems to crash and lock up my Emacs connections, so I’m back to using Jedi…for now. See this article.

(packages-install '( elpy
                     nose
                     jedi
                     py-autopep8          ;; pylint
                     virtualenvwrapper))

Virtual Environments

All development for Python is done in virtual environments. However, this is a monstrous collection of layers, so I am now using pyenv for all my Pythonic virtualization needs, as it does a better job of both virtualenvwrapper and autoenv:

brew install pyenv pyenv-virtualenv pyenv-virtualwrapper

Or, if on Linux, let’s do it neckbeard-style:

git clone https://github.com/yyuu/pyenv.git ~/.pyenv
git clone https://github.com/yyuu/pyenv-virtualenv.git ~/.pyenv/plugins/pyenv-virtualenv

Next, use pip to install virtualenv globally.

sudo pip install virtualenv

And use them by configuring our .profile.

For a given project, we first install a particular Python version for it using the pyenv command (which must be done prior to starting a new virtual environment with the mkvirtualenv command):

pyenv install 2.6.6    # pyenv versions to see what is installed

Get path to this built/installed executable:

pyenv local 2.6.6
pyenv which python

Each project (environment) will be named, and the version of Python can be specified based on the results of the pyenv which command above, for instance:

pyenv virtualenv 2.6.6 lab

And to use the environment in a shell, issue:

pyenv activate lab

Or, better yet, use the local option to make that environment active whenever you enter that directory:

pyenv local lab

Now, commands like pip should be isolated to that virtual environment as well as the needed version.

The Elpy Project deals with the virtualenvwrapper, so call function, M-x pyvenv-workon, to activate a virtual environment, however, we will want to check out pyenv-mode to see if will help.

Basics

WSGI files are just Python files in disguise, so tell them to use the Python environment:

(add-to-list 'auto-mode-alist '("\\.wsgi$" . python-mode))

Careful with the tabs, my friend.

(setq-default indent-tabs-mode nil)
(setq-default tab-width 4)

(add-hook 'python-mode-hook '(lambda () (setq python-indent 4)))

Need to color the defined variables:

(add-hook 'python-mode-hook 'color-identifiers-mode)

Prettify

That self business in Python is quite distracting.

(when (fboundp 'global-prettify-symbols-mode)
  (add-hook 'python-mode-hook
            (lambda ()
              (push '("self" . ?◎) prettify-symbols-alist)
              (modify-syntax-entry ?. "."))))

ELPY

According to the ELPY Web Site, we first install the python-based package components:

pip install jedi

# flake8 for code checks ... which installs pep8
pip install flake8

# and importmagic for automatic imports
pip install importmagic

pip install elpy

Once this has been installed, we can enable it:

(when (require 'elpy nil t)
  (elpy-enable))

Lint

My company has standardized on the pep8 project, just make sure you’ve install the Flake8 library:

workon wpc # Or whatever the project name is
pip install --upgrade flake8

Flycheck automatically supports Python with Flake8. To use it, set the virtual environment, and the errors should appear automatically.

Nose

Unit test and code coverage tool for Python now comes to Emacs with Python Nose.

(require 'nose nil t)

Jedi

Auto-completion system for Python. This code hooks Jedi into the standard Python mode. See these instructions for details (but this should have been installed for Elpy).

pip install jedi

New keys:

  • C-Tab for auto complete.
  • C-. to jump to definition (overrides the ctags interface)
  • C-c d to show the function documentation
(when (require 'jedi nil t)
      (add-hook 'python-mode-hook 'jedi:setup)
      (add-hook 'python-mode-hook 'jedi:ac-setup)
      (setq jedi:setup-keys t)
      (setq jedi:complete-on-dot t))

Technical Artifacts

Make sure that we can simply require this library.

(provide 'init-python)

Before you can build this on a new system, make sure that you put the cursor over any of these properties, and hit: C-c C-c