can not execute a custom function which has python script inside it: no python provider found

[jdhao]

• nvim --version: 0.4.0
• Vim (version: 7.4): behaves differently
• Operating system/version: CentOS 7.4
• Terminal name/version: mintty terminal, 3.0.0
• $TERM: xterm-256color

Steps to reproduce

Using the following minimal init.vim:

function! RandomInt(maxLen)
python << EOF
import vim
import random

idx = random.randint(0, int(vim.eval('a:maxLen')))
vim.command("let index = %s"% idx)
EOF
echo index
endfunction

1. open neovim with the above setting:

nvim -u init.vim

2. using the following command in command mode:

call RandomInt(10)

Actual behaviour

I got an error. The error message is:

Error detected while processing function RandomInt:
line 7:
E319: No "python" provider found. Run ":checkhealth provider"
line 8:
E121: Undefined variable: index

For reference, the output of :checkhealth provider:

health#provider#check
========================================================================
## Clipboard (optional)
  - WARNING: No clipboard tool found. Clipboard registers (`"+` and `"*`) will not work.
    - ADVICE:
      - :help clipboard

## Python 2 provider (optional)
  - INFO: Disabled (g:loaded_python_provider=1).  This might be due to some previous error.
  - WARNING: No Python executable found that can `import neovim`. Using the first available executable for diagnostics.
  - ERROR: Python provider error:
    - ADVICE:
      - provider/pythonx: Could not load Python 2:
          /bin/python2 does not have the "neovim" module. :help provider-python
          /bin/python2.7 does not have the "neovim" module. :help provider-python
          python2.6 not found in search path or not executable.
          /home/haojiedong/tools/anaconda3/bin/python is Python 3.6 and cannot provide Python 2.
  - INFO: Executable: Not found

## Python 3 provider (optional)
  - INFO: `g:python3_host_prog` is not set.  Searching for python3 in the environment.
  - INFO: Executable: /home/haojiedong/tools/anaconda3/bin/python3
  - INFO: Python version: 3.6.5
  - INFO: pynvim version: 0.3.2
  - OK: Latest pynvim is installed.

## Ruby provider (optional)
  - WARNING: `ruby` and `gem` must be in $PATH.
    - ADVICE:
      - Install Ruby and verify that `ruby` and `gem` commands work.

## Node.js provider (optional)
  - WARNING: `node` and `npm` (or `yarn`) must be in $PATH.
    - ADVICE:
      - Install Node.js and verify that `node` and `npm` (or `yarn`) commands work.

It shows that Python3 is found.

But if I use the above minimal setting with vim, I can call the function and get a random number.

Expected behaviour

I can execute the function without error.

[mhinz]

Well, :checkhealth provider says:

  - INFO: Disabled (g:loaded_python_provider=1).  This might be due to some previous error.

So, have you set that option or was it Nvim? In any case, Nvim considers Python 2 support to be disabled, so the behaviour that I would expect, is that it wouldn't even try to execute your function in the first place.

[jdhao]

No, in the init.vim, there is only the function definition. Do you mean I have to add the following setting:

let g:loaded_python_provider=0

and install python2 in my system? Possibly also set the g:python2_host_prog?

[mhinz]

I think you're confused by the fact that :python means Python 2. That is disabled (apparently it's not installed) on your system.

For Python 3, use :python3 instead.

Also consider changing the function to function! RandomInt(maxLen) abort, so it stops at the very first error, so you won't even see the E121: Undefined variable: index when :python already fails.

[jdhao]

Changing from python << EOF to python3 << EOF works.

But it seems that I can not make python2 work. I am using Anaconda3. I create a python2 virtual environment and install pynvim inside that environment.

Then I use the following settings:

function! RandomInt(maxLen)
python << EOF
import vim
import random

idx = random.randint(0, int(vim.eval('a:maxLen')))
vim.command("let index = %s"% idx)
EOF
echo index
endfunction

let g:loaded_python_provider=0
let g:python_host_prog=expand('~/tools/anaconda3/envs/python2/bin/python')

After that, I start nvim with nvim -u init.vim in the virtual environment. The output of :checkhealth provider is:

health#provider#check
========================================================================
## Clipboard (optional)
  - WARNING: No clipboard tool found. Clipboard registers (`"+` and `"*`) will not work.
    - ADVICE:
      - :help clipboard

## Python 2 provider (optional)
  - INFO: Disabled (g:loaded_python_provider=0).  This might be due to some previous error.
  - INFO: Using: g:python_host_prog = "/home/haojiedong/tools/anaconda3/envs/python2/bin/python"
  - INFO: Executable: /home/haojiedong/tools/anaconda3/envs/python2/bin/python
  - INFO: Python version: 2.7.16
  - INFO: pynvim version: 0.3.2
  - OK: Latest pynvim is installed.

## Python 3 provider (optional)
  - INFO: `g:python3_host_prog` is not set.  Searching for python3 in the environment.
  - INFO: Executable: /home/haojiedong/tools/anaconda3/bin/python3
  - INFO: Python version: 3.6.5
  - INFO: pynvim version: 0.3.2
  - OK: Latest pynvim is installed.

## Ruby provider (optional)
  - WARNING: `ruby` and `gem` must be in $PATH.
    - ADVICE:
      - Install Ruby and verify that `ruby` and `gem` commands work.

## Node.js provider (optional)
  - WARNING: `node` and `npm` (or `yarn`) must be in $PATH.
    - ADVICE:
      - Install Node.js and verify that `node` and `npm` (or `yarn`) commands work.

It seems that python2 is still not loaded for some unknown reasons. So I can not call the function inside virtual env (still errors).

[mhinz]

You should only set g:loaded_python_provider when you want to disable the Python provider on purpose. Now Nvim thinks that it tried to load the Python provider, but failed doing so.

[jdhao]

Thanks for your kind explanations. Removing the line about loaded_python_provider works.