Switch Python Version for Vim & Syntastic

Question

Is it possible to change the python version used by syntastic for syntax checking?

As the Issue https://github.com/scrooloose/syntastic/issues/385 indicates I could use virtual-env. But is it also possible just with syntastic or vim commands?

Klaus

Answer 1

The below is no longer necessary, and might screw up if you're forced to work on a strictly python 2.x script.

The best option is to leave the Syntastic defaults alone, and to use conda to manage separate environments for python 3 and 2 (each with their own version-specific installs of flake8, pyflakes, etc), and to switch to the appropriate environment to edit each file. Syntastic will then call python/flake8/whatever else according to the paths set in the activated environment.

---

From the Syntastic repository README:

Q. The python checker complains about syntactically valid Python 3 constructs...

A. Configure the python checker to call a Python 3 interpreter rather than Python 2, e.g:

let g:syntastic_python_python_exec = '/path/to/python3'

Add that line to your .vimrc - that should fix your problem.

Sphere

Doesn't work for me, with syntastic de5e025ef0b8a9eec588d618ebaebd104945af4c. I'm getting syntax errors from valid Python 3 constructs. :!python3 -m flake8 % works fine. – Stiletto

@Marius Gedminas That fine, since g:syntastic_python_python_exec refers to the python checker, which is unrelated to the flake8 checker. If you want to run flake8 under Python 3 either install a flake8 compiled against Python 3, or write a wrapper script, or set g:syntastic_python_flake8_exe (not *_exec, see the manual for the difference) to 'python3 -m flake8'. – Nellie

I'm now using these settings, which uses either the system python or the python defined by whatever virtualenv I'm in - I use a virtualenv for my python3 work: let g:syntastic_python_checkers=['pylint'] let g:syntastic_python_python_exec = 'python' let g:syntastic_python_pylint_exe = 'python -m pylint' Obviously, I use pyflakes rather than flake8... – Gibbous

For me it makes Syntastic completely blind to any BS I hand to it. – Cadena

Also, I think that this solution interferes with virtualenvs. – Cadena

@BłażejMichalik: well, are you handing it the path to the virtualenv version of python? BTW, ditch virtualenv, and move to conda. – Sphere

Please note that this is no longer the recommended approach these days. Just install virtualenv or pyenv, install the relevant checkers inside, and run Vim from the virtual environment (cf. FAQ). This has the advantage that it works for all Python checkers, not just for python. – Nellie

Answer 2

Easiest solution:

Add this to you .vimrc

 let g:syntastic_python_python_exec = 'python3'
 let g:syntastic_python_checkers = ['python']

This is the straightforward solution to switch to python3.

Toombs

For those of us who only work in Python3 (especially when using Docker to contain the environment), this is much more convenient than setting up a virtual environment just to run Vim. – Fundus

For virtualenv users: If you just set it as 'python', it actually works for the activated python version. – Wingfield

How did this get 24 upvotes if it doesn't work? There is no python checker named "python3". Adding this line will turn off all python syntax checking. – Tanguay

on some Linux distros python 3 executable is called "python3" – Kobarid

@rubystallion Thanks for the feedback. I changed the answer – Toombs

Answer 3

In spite of all the answers here, I still find the recommendation from the FAQ to be the best. I have added this to my .vimrc so that I can easily switch between python versions.

function Py2()
  let g:syntastic_python_python_exec = '/usr/local/bin/python2.7'
endfunction

function Py3()
  let g:syntastic_python_python_exec = '/usr/local/bin/python3.6'
endfunction

call Py3()   " default to Py3 because I try to use it when possible

With those functions installed, it's easy to switch python version right within vim with :call Py2() or :call Py3() depending on what I need at the moment. No need to exit vim and activate a different virtualenv as the popular answer would have you do.

Closer

Answer 4

I managed to convince Syntastic to handle Python 3 syntax with

pip3 install --user flake8

(to make python3 -m flake8 *.py work) and then, in vim:

let g:syntastic_python_flake8_exec = 'python3'
let g:syntastic_python_flake8_args = ['-m', 'flake8']

Stiletto

... Except (1) this doesn't affect the python checker, and (2) it makes syntastic believe flake8 is installed even when it isn't. Set g:syntastic_python_flake8_exe (not exec) to 'python3 -m flake8' if you insist to do it this way. – Nellie

Thank you; apparently I forgot that flake8 wasn't the default Python checker in Syntastic! – Stiletto

You probably meant let g:syntastic_python_flake8_exec = 'python3'. Right? – Barri

Oops, yes, thank you! Although today I use command! -bar Python2 let g:syntastic_python_flake8_exe = 'python2 -m flake8' | SyntasticCheck and command! -bar Python3 let g:syntastic_python_flake8_exe = 'python3 -m flake8' | SyntasticCheck – Stiletto

I'm using pyenv and this answer worked perfectly for me. Thanks! – Muscadel

Answer 5

Not really, but you can get the python3 incompatible warning by install this package.

Let's say your current Syntastic Python checker is python and you want to get python3 incompatible warning. In command mode, you can add py3kwarn to g:syntastic_python_checkers by

:let g:syntastic_python_checkers=['python', 'py3kwarn']

and switch to python2.x only

:let g:syntastic_python_checkers=['python']

Steamroller

but this just works for a vim that is using python 2. I have exactly the reverse problem! Still it is a begining! thx – Klaus

Upvoting because I needed to set vim to use python27, instead of the system default 26 and the accepted answer did not work. let g:syntastic_python_checkers=['python27'], did. – Prokofiev

Answer 6

If you working under virtualenv, you can use a script that detects current python version and invokes flake8 accordingly. Put the following somewhere in your path and name is flake8.sh:

#!/bin/sh
PYMAJOR=$(python --version | awk '{print $2}'| awk -F. '{print $1}')
exec "/usr/bin/python$PYMAJOR" /usr/bin/flake8 "$@"

Now in you vimrc add:

let g:syntastic_python_flake8_exe='flake8.sh'

Also make sure that both python-flake8 and python3-flake8 (on Ubuntu) are installed.

Mctyre

Answer 7

Only I did to fix this was to do:

  let g:syntastic_python_flake8_exec = '/path/to/python3'

To make sure flake8 is synced with Python3's syntax. Even when I'm in a virtualenv works.

Therese

Answer 8

Just to iterate on Zaar Hai's script a bit, something like this should work and be a bit more robust.

#!/usr/bin/env bash

_python=$(command -v python)

[[ "$(uname -s)" =~ Darwin ]] && IS_OSX=true

if [[ "$IS_OSX" ]]; then
    if command -v 'greadlink' >/dev/null 2>&1; then
        greadlink -f "$_python"
    else
        echo 'Install coreutils!' >&2
    fi
else
    readlink -f "$_python"
fi

Noblenobleman