Python Development Configuration

• python-mode
• lsp-mode
• Debugging with dap-mode
• Running tests with Projectile
• Using virtualenv

https://github.com/mikf/gallery-dl

pip install -r requirements.txt

(use-package python-mode
  :ensure nil
  :custom
  (python-shell-interpreter "python3"))

Commands:

• Interactive Python shell: M-x run-python (C-c C-p or g z in evil-mode)
• python-shell-send-file (C-c C-l)
• python-shell-send-buffer (C-c C-c)
• python-shell-send-region (C-c C-r)

https://emacs-lsp.github.io/lsp-mode/page/languages/

pip install --user python-language-server[all]

Ensure that it’s on the PATH! If not, you may need to add ~/.local/bin to PATH

We are starting with the lsp-mode configuration from “Build Your Own IDE with lsp-mode”, check that out for more details on lsp-mode!

:hook (python-mode . lsp-deferred))

If you see an error complaining about company-capf, this may be a bug with lsp-mode.

As a workaround, run package-reinstall to reinstall lsp-mode and lsp-ui packages and then restart Emacs.

Using pytest:

pip install pytest

Skip test_results.py, it’s slow!

Use Projectile’s projectile-test-project command:

• Set a directory-local variable for projectile-project-test-cmd with add-dir-local-variable
• Set compilation-read-command to nil to skip asking every time you want to run the test (might be unsafe!)
• You can use g r inside of the unit test buffer to rerun the tests or call recompile interactively

Induce a failure!

I recommend watching “Emacs IDE - How to Debug Your Code with dap-mode” to learn more about the features!

Configuration instructions: https://emacs-lsp.github.io/dap-mode/page/configuration/#python

However, we will use debugpy (ptvsd is deprecated):

pip install debugpy

(dap-python-debugger 'debugpy)

Run dap-debug and select the pytest configuration. Fails due to python2!

Set dap-python-executable to python3

(dap-python-executable "python3")

Running the default pytest configuration doesn’t launch from the correct path, let’s edit the configuration with dap-debug-edit-template:

(dap-register-debug-template
  "Python :: Run pytest (gallery-dl)"
  (list :type "python"
        :cwd "/home/daviwil/Projects/Code/gallery-dl"
        :module "pytest"
        :request "launch"
              :debugger 'debugpy
        :name "Python :: Run pytest (gallery-dl)"))

However, this still doesn’t work correctly from within a file in the project folder. dap-mode bug?

This part is only necessary if you use virtualenv in your Python development workflow!

virtualenv env
. env/bin/activate

Use pyvenv for setting up the right virtualenv in Emacs:

(use-package pyvenv
  :config
  (pyvenv-mode 1))

Run pyvenv-activate and select the env folder, now lsp-mode and dap-mode will use it!