hope you are all well.

Before stating problem, let me tell you my setup. I am using Emacs 27.1, using pyvenv, projectile, lsp-mode, lsp-python-ms for python-mode. I have set WORKON_HOME environmental variable to ~/.pyenv/versions and created an env named venv3.8. I can activate the venv using <M-x> pyvenv-workon <RET> venv3.8 <RET>. After that i can start lsp with lsp command.

My idea was to set virtualenv (using pyvenv-workon) automatically upon opening a project (python project) or opening a python script (not part of a project). So the concept was like this -

  1. If a project is opened, meaning projectile-project-name is available first check if there is a virtualenv with the same name, if thats available activate it. If thats not available check a special variable (which i set with defcustom) name python-env-name for a hint, now if the specified env is available then activate it. Else do nothing.
  2. If a standalone script is opened, then check if pyhton-env-name for a hint, if the specified env is available, activate it. Else do nothing.
  3. After activating the virtualenv, start lsp-mode.

The custom variable python-env-name is supposed to be available to set in a .dir-local.el so that i can easily set per project venv if necessary.

Here is my current code -

(defcustom python-env-name "venv"
  "Set the virtualenv name to be used.

The virtualenv name is the folder name of a virtualenv
located under WORKON_HOME directory.  It is set to be
  :type 'string
  :tag "Python Virtual Environment Name"
  :group 'python
  :safe 'stringp)

(defun my/log (message)
  "Log MESSAGE to *my-logs* buffer.

MESSAGE is string value."
  (interactive "sMessage: ")
  (if (stringp message)
      (with-current-buffer (get-buffer-create "*my-logs*")
        (insert message))))

(defun my/activate-venv-for-project ()
  "Activates virtualenv for current project."
  (let ((project-venv-path (concat (getenv "WORKON_HOME") "/"
        (default-venv-path (concat (getenv "WORKON_HOME") "/"
                                   (buffer-local-value 'python-env-name (current-buffer)))))
    (my/log (format "Project venv: %s, found: %s\n" project-venv-path
                    (file-directory-p project-venv-path)))
    (my/log (format "Default venv: %s, found: %s\n" default-venv-path
                    (file-directory-p default-venv-path)))
    (if (file-directory-p project-venv-path)
        (pyvenv-workon projectile-project-name)
      (if (file-directory-p default-venv-path)
          (pyvenv-workon python-env-name)))))

(defun my/activate-venv-for-script ()
  "Activate virtualenv for a standalone script."
  (let ((default-venv-path (concat (getenv "WORKON_HOME") "/"
                                   (buffer-local-value 'python-env-name (current-buffer)))))
    (my/log (format "Script default venv: %s, found: %s\n" default-venv-path
                    (file-directory-p default-venv-path)))
    (if (file-directory-p default-venv-path)
        (pyvenv-workon python-env-name))))
(defun my/setup-python-environment ()
  "Setup the python virtual env for project or python script.

This function first checks if we opened a project, if so either the
virtualenv named as the projectile-project-name or the value of
python-env-name will be used to activate virtualenv.  If none are
aviable no virtualenv will be activated.  If we didnt open any
project, then simply check the python-env-name variable, if
the env is available then activate it or not.  Afterwards it will
start up lsp-mode."
  (if (bound-and-true-p projectile-project-name)
  (require 'lsp-python-ms)

(add-hook 'python-mode-hook 'my/setup-python-environment)

As you can see, i tried to show some message while setting up the environment. Then i opened a python project (using projectile), and opened a python file. I have already set the python-env-name in a dir-local file as follows -

((python-mode . ((python-env-name . "venv3.8"))))

Here is the text from *my-logs* buffer -

Project venv: ~/.pyenv/versions/python-check, found: nil
Default venv: ~/.pyenv/versions/venv, found: nil

So clearly, the dir-local value is not used in the my/setup-python-environment. But if i put the cursor at the python file and run <M-x> eval-expression <RET> python-env-name <RET> it shows "venv3.8" in the minibuffer. So the dir local variables are read. What am i doing wrong? Please help. Forgive my if i am doing anything wrong as i am very new to elisp. Thanks in advance. I hope i was clear enough.


1 Answer 1


Local variables are set after hooks are run. Try using a timer:

(let ((buf (current-buffer)))
  (run-with-timer 0.01 nil
          (lambda ()
            (with-current-buffer buf
              (if (bound-and-true-p projectile-project-name)
              (require 'lsp-python-ms)
  • I tried the timer solution, but got an error saying buf is void variable.
    – shimon
    Oct 18, 2020 at 10:54
  • Is lexical binding enabled?
    – Nova
    Oct 18, 2020 at 11:16

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