How do I change backend for company?

Question

Recently I have discovered tabnine, a really good completion backend. I wanted to use it in emacs. So I went through the installation procedure and now I have it. But when I M-x company-diag, it shows me that I am using company-yasnippet in major mode python. I want to use tabnine instead. How do I do that?

Emacs 27.1 (x86_64-pc-linux-gnu) of 2020-08-28 on juergen
Company 0.9.13

company-backends: ((company-anaconda)
 company-capf company-yasnippet company-tabnine)

Used backend: company-yasnippet
Major mode: python-mode

This is company-diag.

Answer 1

A few things.

1. company decides its backend based on the variable company-backends. If you want a specific auto-completion backend, you must specify it in your init.el file.

In general, you can read documentation on variables by using M-x apropos-variable.

2. To add a backend to company, call (add-to-list 'company-backends '(<backend name>))

For example, to add Elisp completion, there is a backend called company-elisp that comes with company.

To use this, you run (add-to-list 'company-backend '(company-elisp)).

This will add company-elisp to the list of backends that company decides to use.

3. Company runs through its list of backends in company-backends and performs a test to see if it should run a given backend for your current mode.

The first to pass the test is used. All others are ignored.

Now, looking at company-anaconda, it recommends:

(eval-after-load "company"
  '(add-to-list 'company-backends 'company-anaconda))

or, if you want both company-anaconda and company-capf together:

(eval-after-load "company"
 '(add-to-list 'company-backends '(company-anaconda :with company-capf)))

Finally, you must add: (add-hook 'python-mode-hook 'anaconda-mode)

Looking at the source code for company-anaconda reveals that you must enable anaconda-mode for company to choose the company-anaconda backend.