VIM and Python – a Match Made in Heaven

It has come to my attention that somebody ‘round these parts has been preaching the gospel of Sublime Text 3. Well, as the resident senior developer (err, old fogey), I feel it’s my duty to provide a counterexample by way of the only TRUE Python development environment you will ever need – and that environment is of course VIM. That’s right. VIM is ubiquitous, fast, and never crashes. And it can do just about anything!

On the down side though, VIM can be a pain to configure, but fear not – This article will show you how to get a powerful VIM environment setup, geared towards wrangling Python day in and day out.

To get the most out of this article you should have at least a basic understanding on how to use VIM and its command modes. If you’re just getting started, check out this resource or this one. Spend some time with it before moving on.

Installing

Since VIM comes pre-installed on a number of *nix systems, let’s first and foremost check to see if it’s installed:

vim --version

If installed, you should see something like:

VIM - Vi IMproved 7.3 (2010 Aug 15, compiled Nov  5 2014 21:00:28)
Compiled by [email protected]
Normal version without GUI.  Features included (+) or not (-):
-arabic +autocmd -balloon_eval -browse +builtin_terms +byte_offset +cindent
-clientserver -clipboard +cmdline_compl +cmdline_hist +cmdline_info +comments
-conceal +cryptv +cscope +cursorbind +cursorshape +dialog_con +diff +digraphs
-dnd -ebcdic -emacs_tags +eval +ex_extra +extra_search -farsi +file_in_path
+find_in_path +float +folding -footer +fork() -gettext -hangul_input +iconv
+insert_expand +jumplist -keymap -langmap +libcall +linebreak +lispindent
+listcmds +localmap -lua +menu +mksession +modify_fname +mouse -mouseshape
-mouse_dec -mouse_gpm -mouse_jsbterm -mouse_netterm -mouse_sysmouse
+mouse_xterm +multi_byte +multi_lang -mzscheme +netbeans_intg -osfiletype
+path_extra -perl +persistent_undo +postscript +printer -profile +python/dyn
-python3 +quickfix +reltime -rightleft +ruby/dyn +scrollbind +signs
+smartindent -sniff +startuptime +statusline -sun_workshop +syntax +tag_binary
+tag_old_static -tag_any_white -tcl +terminfo +termresponse +textobjects +title
 -toolbar +user_commands +vertsplit +virtualedit +visual +visualextra +viminfo
+vreplace +wildignore +wildmenu +windows +writebackup -X11 -xfontset -xim -xsmp
 -xterm_clipboard -xterm_save
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
      user exrc file: "$HOME/.exrc"
  fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -c -I. -D_FORTIFY_SOURCE=0 -Iproto -DHAVE_CONFIG_H -arch i386 -arch x86_64 -g -Os -pipe
Linking: gcc -arch i386 -arch x86_64 -o vim -lncurses

At this point, you want to look for two things-

1. The VIM version. This should be > 7.3.
2. Python Support. Under the list of features, make sure you see +python.

If you have both of these, then move right along to VIM Extensions. If not, it’s time to install/upgrade.

OSX

Grab Homebrew, if you don’t already have it, and run:

$ brew update
$ brew install vim

*NIX

For Debian or Ubuntu you can try:

$ sudo apt-get remove vim-tiny
$ sudo apt-get update
$ sudo apt-get install vim

For other flavors of Linux check the docs from your package manager. Here is a link to get you started: Install Vim

Windows

There are many different ways to install VIM on Windows. Start with the official docs.

Verifying the Install

Make sure you have installed VIM > 7.3 with Python support. Again, run vim --version to verify this. If you want to check the specific version of Python used in VIM, run :python import sys; print(sys.version) from within VIM:

2.7.6 (default, Sep  9 2014, 15:04:36)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)]

This should output your current version of Python. If you get an error, then you don’t have Python support and you either need to reinstall or recompile if you’re building from source.

With VIM installed, let’s look at how to customize VIM for Python development.

VIM Extensions

VIM can do a lot of what developers need right out of the box. However, VIM is also massively extensible and there are some pretty killer extensions that make VIM behave more like a “modern” IDE. So, the very first thing you need is a good extension manager.

Extensions in VIM are often referred to as bundles or plugins.

Vundle

VIM has several extension managers, but the one we strongly recommend is Vundle. Think of it as pip for VIM. It makes installing and updating packages trivial.

Let’s get Vundle installed:

$ git clone https://github.com/gmarik/Vundle.vim.git ~/.vim/bundle/Vundle.vim

This command downloads the Vundle plugin manager and chucks it in your VIM bundles directory. Now you can manage all your extensions from the .vimrc configuration file.

Add the file to your user’s home directory:

$ touch ~/.vimrc

Now set up Vundle in your .vimrc by adding the following to the top of the file:

set nocompatible              " required
filetype off                  " required

" set the runtime path to include Vundle and initialize
set rtp+=~/.vim/bundle/Vundle.vim
call vundle#begin()

" alternatively, pass a path where Vundle should install plugins
"call vundle#begin('~/some/path/here')

" let Vundle manage Vundle, required
Plugin 'gmarik/Vundle.vim'

" Add all your plugins here (note older versions of Vundle used Bundle instead of Plugin)


" All of your Plugins must be added before the following line
call vundle#end()            " required
filetype plugin indent on    " required

That’s it. You’re now set up to use Vundle. Afterward you can add the plugins you want to install, then fire up VIM and run:

:PluginInstall

This command tells Vundle to work its magic – downloading all the plugins and installing/updating them for you.

For Windows users, check out the Windows Installation Instructions.

Let’s make an IDE

We couldn’t possibly list all the VIM features, but let’s look at a quick list of some of the powerful out-of-the-box features perfect for Python development.

Ditch the Mouse

Probably the MOST important feature of VIM is that it doesn’t require a mouse (except for the graphical variants of VIM). At first this may seem like a horrible idea, but after you invest the time – and it does take time – to learn the key combinations, you will speed up your overall workflow!

Split Layouts

Open a file with :sv <filename> and you split the layout vertically (e.g., the new file opens below the current file) or reverse the keys to :vs <filename> and you get a horizontal split (e.g., the new file opens to the right of your current file).

You can nest splits as well, so you can have splits inside of splits, horizontal and vertical, to your heart’s content. As we all know we often need to look at several files at once when developing.

Pro Tip: Make sure to utilize tab completion to find files after typing :sv.

Pro Tip: You can also specify different areas of the screen where the splits should occur by adding the following lines to the .vimrc file:

set splitbelow
set splitright

Pro Tip: Want to move between the splits without using the mouse? Simply add the following to .vimrc and you can jump between splits with just one key combination:

"split navigations
nnoremap <C-J> <C-W><C-J>
nnoremap <C-K> <C-W><C-K>
nnoremap <C-L> <C-W><C-L>
nnoremap <C-H> <C-W><C-H>

Key combos:

• Ctrl-j move to the split below
• Ctrl-k move to the split above
• Ctrl-l move to the split to the right
• Ctrl-h move to the split to the left

In other words, press Ctrl plus the standard VIM movement key to move to a specific pane.

But wait what is the nnoremap thing? – in a nutshell nnoremap remaps one key combination to another; the no part means remap the key in normal mode as opposed to visual mode. Basically nnoremap <C-J> <C-W><C-j> says in normal mode when I hit <C-J> do <C-W><C-j> instead. More info can be found here.

Buffers

While VIM can do tabs, many prefer buffers and splits. You can think of a buffer as a recently opened file. VIM provides easy access to recent buffers, just type :b <buffer name or number> to switch to an open buffer (autocomplete works here as well). You can also use :ls to list all buffers.

Pro Tip: At the end of the :ls output, VIM will prompt with Hit enter to continue. You can instead type :b <buffer number> and pick the buffer immediately while you still have the list displayed (which saves a keystroke and having to remember the buffer number).

Code Folding

Most “modern” IDEs provide a way to collapse (or fold) methods and classes, showing you just the class/method definition lines instead of all the code.

You can enable that in .vimrc with the following lines:

" Enable folding
set foldmethod=indent
set foldlevel=99

This works all right, but you have to type za to fold (and unfold). The space key would be much better. So add this line to your .vimrc file as well:

" Enable folding with the spacebar
nnoremap <space> za

Now you can easily hide portions of your code that you’re not currently working on.

The initial command, set foldmethod=indent, creates folds based upon line indents. This however often creates more folds that you really want. But have no fear! There are several extensions that attempt to rectify that. We recommend SimpylFold. Install it with Vundle by adding the following line to .vimrc

Plugin 'tmhedberg/SimpylFold'

Don’t forget to install the plugin – :PluginInstall.

Pro Tip: Want to see the docstrings for folded code?

let g:SimpylFold_docstring_preview=1

Python Indentation

Of course for code folding to work based on indentations, you want your indents to be correct. Again VIM falls short a bit out of the box because it doesn’t handle auto-indent after a function definition. Two things can be done with indentation:

1. The first is to get indentation to follow PEP8 standards.
2. The second part is to better handle auto-indentation.

PEP8

To add the proper PEP8 indentation, add the following to your .vimrc:

au BufNewFile,BufRead *.py:
    \ set tabstop=4
    \ set softtabstop=4
    \ set shiftwidth=4
    \ set textwidth=79
    \ set expandtab
    \ set autoindent
    \ set fileformat=unix

This will give you the standard four spaces when you hit tab, ensure your line length doesn’t go beyond 80 characters, and store the file in a unix format so you don’t get a bunch of conversion issues when checking into GitHub and/or sharing with other users.

And for full stack development you can use another au command for each filetype:

au BufNewFile,BufRead *.js, *.html, *.css:
    \ set tabstop=2
    \ set softtabstop=2
    \ set shiftwidth=2

This way you can have different settings for different filetypes. There is also a plugin called ftypeswhich will allow you to have a separate file for each filetype you want to maintain settings for, so use that if you see fit.

Auto-Indentation

Autoindent will help but in some cases (like when a function signature spans multiple lines), it doesn’t always do what you want, especially when it comes to conforming to PEP8 standards. To fix that, we can use the indentpython.vim extension:

Plugin 'vim-scripts/indentpython.vim'

Flagging Unnecessary Whitespace

We also want to avoid extraneous whitespace. We can have VIM flag that for us so that it’s easy to spot – and then remove.

define BadWhitespace before using in a match.

highlight BadWhitespace ctermbg=red guibg=darkred 
au BufRead,BufNewFile *.py,*.pyw,*.c,*.h match BadWhitespace /\s\+$/

This will mark extra whitespace as bad, and probably color it red.

UTF8 Support

For the most part, you should be using UTF8 when working with Python, especially if you’re working with Python 3. Make sure VIM knows that with the following line:

set encoding=utf-8

Auto-complete

The best plugin for Python auto-complete is YouCompleteMe. Again, use Vundle to install:

Bundle 'Valloric/YouCompleteMe'

Under the hood YouCompleteMe uses a few different auto-completers (including Jedi for Python), and it needs some C libraries to be installed for it to work correctly. The docs have very good installation instructions so I won’t repeat them here, but be sure you follow them.

It works out of the box pretty well, but let’s add a few customizations:

let g:ycm_autoclose_preview_window_after_completion=1
map <leader>g  :YcmCompleter GoToDefinitionElseDeclaration<CR>

The former line ensures that the autocomplete window goes away when you’re done with it, and the latter defines a shortcut for goto definition.

My leader key is mapped to space, so space-g will goto definition of whatever I’m currently on. Helpful when exploring new code.

Virtualenv Support

One issue with the goto definition above is that VIM by default doesn’t know anything about virtualenv, so you have to make VIM and YouCompleteMe aware of your virtualenv by adding the following lines of code to .vimrc:

"python with virtualenv support
py << EOF
import os
import sys
if 'VIRTUAL_ENV' in os.environ:
  project_base_dir = os.environ['VIRTUAL_ENV']
  activate_this = os.path.join(project_base_dir, 'bin/activate_this.py')
  execfile(activate_this, dict(__file__=activate_this))
EOF

This determines if you are running inside a virtualenv, and then switches to that specific virtualenv and sets up your system path so that YouCompleteMe will find the appropriate site packages.

Syntax Checking/Highlighting

You can have VIM check your syntax on each save with the syntastic extension:

Plugin 'scrooloose/syntastic'

Also add PEP8 checking with this nifty little plugin:

Plugin 'nvie/vim-flake8'

Finally, make your code look pretty:

let python_highlight_all=1
syntax on

Color Schemes

Color schemes work in conjunction with the basic color scheme that you are using. Check out solarized for GUI mode, and Zenburn for terminal mode:

Plugin 'jnurmine/Zenburn'
Plugin 'altercation/vim-colors-solarized'

Then just add a bit of logic to define which scheme to use based upon the VIM mode:

if has('gui_running')
  set background=dark
  colorscheme solarized
else
  colorscheme zenburn
endif

Solarized also ships with a dark and light theme. To make switching between them very easy (by pressing F5) add:

call togglebg#map("<F5>")

File Browsing

If you want a proper file tree then NERDTree is the way to go.

Download and install

git clone https://github.com/scrooloose/nerdtree.git ~/.vim/bundle/nerdtree

With those few lines of code, the plugin is now installed! To open a NERDTree panel, in normal mode, we call :NERDTree.

At this point, we can open any file by typing o, or with the more convenient alias, the Enter key. Unlike the default file browser, this will open the new file directly into the buffer to the right of NERDTree, similar to what you might be used to in a program, like TextMate.

If you ever forget what the correct key is for a particular action, press ? to display a quickie help buffer.

Bookmarks

To expedite the process of navigating through your directory structures, NERDTree allows you to conveniently create bookmarks. Do so by moving the cursor to the directory that you wish to bookmark, and then typing:

:bookmark <desired bookmark name>

With this in place, you can now bring up your list of available bookmarks by pressing B. It’s a huge help!

Menu

Press the letter m to bring up a menu that will allow you to quickly add, move, copy, and delete nodes (or files).

Plugin 'scrooloose/nerdtree'

And if you want to use tabs, utilize vim-nerdtree-tabs:

Plugin 'jistr/vim-nerdtree-tabs'

Want to hide .pyc files? Then add the following line:

let NERDTreeIgnore=['\.pyc$', '\~$'] "ignore files in NERDTree

Super Searching

Want to search for basically anything from VIM? Check out ctrlP:

Plugin 'kien/ctrlp.vim'

As expected, press Ctrl-P to enable the search and then just start typing. If your search matches anything close to the file you’re looking for, it will find it. Oh – and it’s not just files; it will find tags as well! For more, check out this YouTube video.

Line Numbering

Turn on line numbers on the side of the screen with:

set nu

Git Integration

Want to perform basic git commands without leaving the comfort of VIM? Then vim-fugitive is the way to go:

Plugin 'tpope/vim-fugitive'

See it in action on VIMcasts.

Powerline

Powerline is a status bar that displays things like the current virtualenv, git branch, files being edited, and much more.

It’s written in Python, and it supports a number of other environments like zsh, bash, tmux, and IPython.

Plugin 'Lokaltog/powerline', {'rtp': 'powerline/bindings/vim/'}

Take a look at the official docs for all the configuration options.

System clipboard

Vim usually has its own clipboard and ignores the system keyboards, but sometimes you might want to cut, copy, and/or paste to/from other applications outside of VIM. On OSX, you can access your system clipboard with this line:

set clipboard=unnamed

VIM in the Shell

And finally, once you’ve mastered VIM and its keyboard shortcuts, you’ll often find yourself getting annoyed with the lack of those same shortcuts in the shell. Fear not, most shells have a VI mode. To turn it on for your shell, add the following line to ~/.inputrc:

set editing-mode vi

Now you will not only be able to use VIM key combos in the shell, but also in the Python interpreter and any other tool that uses GNU Readline (i.e., most database shells). Now you have VIM everywhere!

Resources

1. VIM Tutor comes with VIM, so once VIM is install just type vimtutor from the command line and the program will teach you how to use VIM by, well, using VIM.
2. VIMcasts are advanced tutorial videos describing how to use many of VIM’s features.
3. Official VIM docs
4. Open Vim
5. Learn Vimscript the Hard Way is perfect for learning vimscript.