Import custom Python modules in Vim plugins

published on June 16, 2016.
Heads-up! You're reading an old post and the information in it is quite probably outdated.

This took me a while to figure out so I’m writing it down for future self and anyone else who needs it.

I started writing a new Vim plugin that will use the Python interface as most of the work will be done there, mostly to keep my sanity.

Having a plugin layout such as:

.
├── lib
│   └── mypymodule
│       └── ham.py
└── plugin
    └── my-vim-plugin.vim

I want to be able to do a

from mypymodule import ham

from within the my-vim-plugin.vim file.

For that to happen the <sfile> command line special comes to rescue. It is the file name of the sourced file in Vim, that is, the file name of the Vim plugin. Using the :p and :h file name modifiers it gives us the full path to the plugin directory of our plugin.

" This will give something like
" /home/robert/projects/my-vim-plugin/plugin
let g:plugin_path = expand('<sfile>:p:h')

And here comes the kicker: the <sfile> needs to be expanded outside of our Vim function where it is used, otherwise the <sfile> points to the path of the file that called the Vim function.

In code, getting the path to the sourced file from within the Vim function would be incorrect:

" ./plugin/my-vim-plugin.vim
function! MyVimPlugin()
python << endpython

import vim

vim.command("let a:plugin_path = expand('<sfile>:p:h')
plugin_path = vim.eval("a:plugin_path")
print plugin_path

endpython
endfunction

because it would end up printing the current working directory from where the MyVimPlugin function is called.

The correct way to do is to get the path to the sourced file outside of the Vim function:

" ./plugin/my-vim-plugin.vim
let g:plugin_path = expand('<sfile>:p:h')

function! MyVimPlugin()
python << endpython

import vim

vim.command("let a:plugin_path = expand('<sfile>:p:h')
plugin_path = vim.eval("a:plugin_path")
print plugin_path

endpython
endfunction

This way the path is set at the time the plugin is sourced and not at the time when function is called.

Finally, to be able to import the mypymodule from the lib, we need to point to the lib directory and add it to the system paths. Complete example:

" ./plugin/my-vim-plugin.vim
let g:plugin_path = expand('<sfile>:p:h')

function! MyVimPlugin()
python << endpython

import os
import sys
import vim

" Get the Vim variable to Python
plugin_path = vim.eval("g:plugin_path")
" Get the absolute path to the lib directory
python_module_path = os.path.abspath('%s/../lib' % (plugin_path))
" Append it to the system paths
sys.path.append(python_module_path)

" And import!
from mypymodule import ham

endpython
endfunction

By the way, here’s the documentation for the Vim Python module.

Happy hackin’!

Tags: vim, python, plugin.
Categories: Programming, Development.

Thanks for reading! If you require help on a project of any kind, let's talk!

Robert Basic

Robert Basic

Software engineer, consultant, open source contributor.

Let's work together!

If you require outsourcing or consulting help on your projects, I'm available!

Robert Basic © 2008 — 2019
Get the feed