Setting up Python for Neovim
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Setting up Python for Neovim
Neovim requires a package to be installed for Python plugins to work. You
really should read
:h nvim-python to supplement the info on this page.
Table of Contents
- A brief overview of Neovim + Python
- Simple Setup
- Using Virtual Environments
- Tips for using pyenv
- Why you shouldn't use sudo
A brief overview of Neovim + Python
The main advantages of using Python in plugins is that it enables plugins to have access to network sockets, and perform long-running or expensive operations in the background without freezing the Vim UI. This is the reason it is commonly used with completion plugins.
Vim plugins are able to execute Python code when Vim is compiled with Python support. However, default system installations of Vim that are compiled with Python versions that are considered to be the stable default for the OS, which usually meant Python 2.6 or 2.7 until recently. Additionally, Vim could only be compiled with Python 2 or Python 3, not both. Re-compiling Vim to include newer versions is a non-trivial task and it would put an undue burden on users if plugins required Python 3.
Neovim resolves these limitations by providing a bridge to your system's Python installations. It requires a Python package to be installed, which still puts a burdern on the user, but it is arguably easier than re-compiling Vim.
Each Python interpreter that is used with Neovim will require the neovim package.
deoplete.nvim requires Python 3 to be installed. By extension,
deoplete-jedi does, too. It is recommended that Python 3.3+ is used, but any
Python version greater than 3.1 should work.
If you do light Python development, or the extent of your Python use is limited to Neovim, the basic installation instructions will be sufficient.
:h nvim-python suggests the use of
sudo pip install neovim for
system-wide availability. It's an acceptable solution if you are certain that
your Python environment will be unaffected. Read the following section before
you consider using
sudo: Why you shouldn't use sudo
It is recommended to use the
--user flag when installing the
pip2 install --user neovim pip3 install --user neovim
--user flag installs
neovim in a directory within your home directory.
The limitation with this is that every user account on the system will need to
perform this step. You can confirm the location and that your environment
permits user packages by running:
python -m site
Using Virtual Environments
If you do heavy Python development, you will most likely prefer using a virtual
deoplete-jedi will display completions for your current shell's
Python interpreter (run:
which python to determine this). This includes the
Python interpreter that are made active using a virtualenv.
If you are already using virtualenv for all of your work, it is recommended
that you use separate virtual environments for Neovim, and only Neovim. This
will remove the need to install the
neovim package in each virtual
environment. The following examples uses pyenv. There are
tips below for installing and using
TODO: add instructions for pyvenv and virtualenv
pyenv install 2.7.11 pyenv install 3.4.4 pyenv virtualenv 2.7.11 neovim2 pyenv virtualenv 3.4.4 neovim3 pyenv activate neovim2 pip install neovim pyenv which python # Note the path pyenv activate neovim3 pip install neovim pyenv which python # Note the path # The following is optional, and the neovim3 env is still active # This allows flake8 to be available to linter plugins regardless # of what env is currently active. Repeat this pattern for other # packages that provide cli programs that are used in Neovim. pip install flake8 ln -s `pyenv which flake8` ~/bin/flake8 # Assumes that $HOME/bin is in $PATH
Now that you've noted the interpreter paths, add the following to your
let g:python_host_prog = '/full/path/to/neovim2/bin/python' let g:python3_host_prog = '/full/path/to/neovim3/bin/python'
Tips for using pyenv
- Ensure you have the prerequisites installed.
- Installing pyenv with homebrew is unreliable. Use pyenv-installer instead.
- There is a final step that's printed to the terminal after installing
pyenvand it's important!
- To confirm you have
pyenvcorrectly installed, run
which pyenv. It should print a shell function, not a file path.
pyenv doctorto avoid surprises.
pyenv globalcan be thought of as altering the
$PATHto include the specified versions'
bindirectory. This only works while
pyenv shellis the same as above, but for the current session.
pyenv localis the same as above, but it writes a
.python-versionfile in the current directory. It allows the specified versions to be automatically set when you enter the directory, and unset when you leave it. Very convenient for projects.
- You will want to add
.python-versionto your global
pyenv shell --unsetwill reset the session's Python versions.
pyenv activate venvnamediffers from
pyenv shell venvnamein that only one
$VIRTUAL_ENVcan be active at a time.
pyenv deactivatedeactivates the virtual environment.
pyenv versionslists the versions you have installed.
systemis a special case pointing to Python versions that were originally found in
$PATH. Virtual environment names are listed as versions.
Why you shouldn't use sudo
Unless you know what you're doing, the system installed Python interpreters
should remain pristine and only contain packages that were installed via the
OS's package manager (read: not pip).
sudo in front of
should make you cringe any time it's recommended.
Some distros use separate locations for system packages and user packages, but
the potential to mess things up is increased when you use
sudo. On distros
that don't make a distinction between system and user packages, it's possible
to upgrade system packages with
sudo pip install -U. Or the reverse could
happen and you'll downgrade packages installed with
pip. There is also the
issue of non-Python system packages that may require the specific versions of
Python packages that were built for the distro. The point is, you will have
two package managers competing to decide what's new or old.
A very common example of what can go wrong:
sudo pip install --upgrade pip.
It is a problem many Python developers encounter. This problem
occurs more than it should and renders all Python programs installed in the
system bin directories to be broken.
If you can't honestly say that you know how Python packages are laid out or what your system's Python dependencies are, and enjoy having a stable, error-free Python installation, leave the system Python installations alone.