Full Python Scripting in Vim
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README.md

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Snake (SNAAAAAAAAAKKKE) is a Python module for Vim that let's you use Python to its fullest extent to enhance Vim.

Here's an example of a helper function, written in Python, using Snake, to toggle the word under your cursor between snake-case and camel-case when you press <leader>c:

import snake

@snake.key_map("<leader>c")
def toggle_snake_case_camel_case():
    """ take the word under the cursor and toggle it between snake-case and
    camel-case """

    word = snake.get_word()

    # is it snake case?
    if "_" in word:
        chunks = word.split("_")
        camel_case = chunks[0] + "".join([chunk.capitalize() for chunk in
            chunks[1:]])
        snake.replace_word(camel_case)

    # is it camel case?
    else:
        # split our word on capital letters followed by non-capital letters
        chunks = filter(None, re.split("([A-Z][^A-Z]*)", word))
        snake_case = "_".join([chunk.lower() for chunk in chunks])
        snake.replace_word(snake_case)

Metal Gear Solid Snake Success

Full API Reference

Some other cool things you can do

Bind a function to a key

When you press the key pattern in key_map, the decorated function will run.

import snake

@snake.key_map("<leader>r")
def reverse():
    snake.replace_word(snake.get_word()[::-1])

Use a function for an abbreviation

A Python function can be expanded dynamically as you type an abbreviation in insert mode.

import snake
import time

snake.abbrev("curtime", time.ctime)

Have a function run for a file type

Sometimes it is convenient to run some code when the buffer you open is of a specific file type.

import snake

@snake.when_buffer_is("python")
def setup_python_folding(ctx):
    ctx.set_option("foldmethod", "indent")
    ctx.set_option("foldnestmax", 2)
    ctx.key_map("<space>", "za")

A context object is passed into the function you wrap. This context allows you to set options, let variables, and create abbreviations and keymaps that apply only to the buffer you just opened, not globally.

Press arbitrary keys as if you typed them

from snake import keys

def uppercase_second_word():
    keys("gg") # go to top of file, first character
    keys("w") # next word
    keys("viw") # select inner word
    keys("~") # uppercase it

Installation

Your Vim version must include +python to use Snake. You can check with :version.

Vundle

Add the following line to your Vundle plugin block of your .vimrc:

Plugin 'amoffat/snake'

And the following lines to the end of the file:

if filereadable(expand("~/.vim/bundle/snake/plugin/snake.vim"))
    source ~/.vim/bundle/snake/plugin/snake.vim
endif

Re-source your .vimrc. Then :PluginInstall

Pathogen

TODO

Neobundle

Add the following line to your Neobundle plugin block of your .vimrc:

NeoBundle 'amoffat/snake'

And the following lines to the end of the file:

if filereadable(expand("~/.vim/bundle/snake/plugin/snake.vim"))
    source ~/.vim/bundle/snake/plugin/snake.vim
endif

Re-source your .vimrc. Then NeoBundleInstall

Where do I write my Snake code?

~/.vimrc.py is intended to be the python equivalent of ~/.vimrc. Snake will load and evaluate it on startup. It should contain all of your Snake initialization code and do any imports of other Snake plugins. If were so inclined, you could move all of your vim settings and options into ~/.vimrc.py as well:

from snake import multi_set_option, let, multi_command

multi_set_option(
    "nocompatible",
    "exrc",
    "secure",

    ("background", "dark"),
    ("textwidth", 80),

    ("shiftwidth", tab),
    ("softtabstop", tab),
    ("tabstop", tab),
    "expandtab",
)

let("mapleader", ",")

multi_command(
    "nohlsearch",
    "syntax on",
)

from snake.plugins import my_rad_plugin

Design Philosophy

Vim is powerful, but its commands and key-bindings are built for seemingly every use case imaginable. It doesn't distinguish between commonly-used and rarely-used. Snake should use that existing foundation of functionality to add structure for commonly-needed operations. For example, many vim users know that yiw yanks the word you're on into a register. This is a common operation, and so it should be mapped to a simple function:

@preserve_state()
def get_word():
    keys("yiw")
    return get_register("0")

Now instead of your plugin containing execute "normal! yiw", it can contain word = get_word()

How do I write a plugin?

If your plugin is a package, create (or symlink) a directory inside ~/.vim/bundle for your plugin. Make this directory a Python package by creating a __init__.py

If your plugin is a simple one-file module, just create or symlink that file into your ~/.vim/bundle directory.

Next Add from snake.plugins import <your_plugin> to ~/.vimrc.py. Finally, Re-source your ~/.vimrc

For plugin API reference, check out api_reference.md.

Can I use a virtualenv for my plugin?

Yes! But it's crazy!

Just include a requirements.txt file in your package directory that contains the pip freeze output of all the dependencies you wish to include. When your module is imported from .vimrc.py, a virtualenv will be automatically created for your plugin if it does not exist, and your plugin dependencies automatically installed.

Virtualenvs that are created automatically will use your virtualenv_wrapper WORKON_HOME environment variable, if one exists, otherwise ~/.virtualenvs. And virtualenvs take the name snake_plugin_<your_plugin_name>.

Gotchas

You may be wondering how snake can allow for different virtualenvs for different plugins within a single Python process. There's a little magic going on, and as such, there are some gotchas.

When a plugin with a virtualenv is imported, it is imported automatically within that plugin's virtualenv. Then the virtualenv is exited. This process is repeated for each plugin with a virtualenv.

What this means is that all of your plugin's imports must occur at your plugin's import time:

GOOD:

from snake import *
import requests

def stuff():
    return requests.get("http://google.com").text

BAD:

from snake import *

def stuff():
    import requests
    return requests.get("http://google.com").text

The difference here is that in the first example, your plugin will have a reference to the correct requests module, because it was imported while your plugin was being imported inside its virtualenv. In the second example, when stuff() runs, it is no longer inside of your plugin's virtualenv, so when it imports requests, it will not get the correct module or any module at all.

There is also the problem of different plugins having different dependency versions. For example, if Snake plugin A depends on sh==1.10 and plugin B depends on sh==1.11, whichever plugin gets loaded first in .vimrc.py will put their sh module into sys.modules. Then, when the other plugin loads, it will attempt to load sh, see it is in sys.modules, and use that instead, instead of looking in its virtualenv.

All of this obviously isn't great, and something better needs to be built to more thoroughly separate virtualenvs from under a single Python process. I think what can happen is, for the SnakePluginHook, if a fullname has more than 3 paths, drop into the virtualenv for the plugin and run imp.find_module. If the module exists, return self as the loader. Repeat the process in load_module except actually imp.load_module. This way, the dependency should be loaded into sys.modules prefixed by the full plugin name snake.plugins.whatever.sh.

Contributing

Read development.md for technical info.

Pull requests

Although Snake is meant to make Vim more scriptable in Python, it is not meant to provide all the nuanced functionality of Vim. PRs for new features will be screened by the value-add of the feature weighed against the complexity added to the api, with favor towards keeping the api simple.

Snake needs a vundle equivalent

I would like to see an import hook that allows this in your .vimrc.py:

from snake import *

something_awesome = __import__("snake.plugins.tpope/something_awesome")

Where the import hook checks if the plugin exists in ~/.vim/snake, and if it doesn't, looks for a repo to clone at https://github.com/tpope/something_awesome