Send to python-shell-interpreter from the project root

Question

How can I tell the shell to always open relative to my project root?

I have the following python project structure:

mypyjunk
├── mypyjunk
│   ├── common.py
│   ├── __init__.py
│   └── jitter.py
├── README.md
└── tests
    ├── __init__.py
    └── test_all.py

And mypyjunk/jitter.py contains:

from mypyjunk.common import constants


def do_things():
    print(constants)

When I open this file and open a shell interpreter with C-c C-p, I try to send the buffer to the interpreter with C-c C-r, it says:

>>> from mypyjunk.common import constants
... 
... 
... def do_things():
...     print(constants)

Traceback (most recent call last):
  File "<string>", line 17, in __PYTHON_EL_eval
  File "/home/user/mypyjunk/mypyjunk/jitter.py", line 1, in <module>
    from mypyjunk.common import constants
ModuleNotFoundError: No module named 'mypyjunk'

Which tells me this shell has an unexpected root directory, eg:

>>> import os
>>> os.getcwd()
'/home/user/mypyjunk/mypyjunk'

Instead of /home/user/mypyjunk/ where my absolute imports would make sense.

What settings do I need to change to tell python-mode or compile-mode to respect the project root? Also, assume I have lots of projects in ~/ so I can't hard-code a path here in my .emacs.d/init.el, without potentially clobbering my other projects.

Answer 1

I don't know if there's a 'nicer' way using already existing stuff in python.el, but if you just want the interpreter to start at the project root while you're within that project, I'd do something like:

(defvar-local my-python-dir-override nil)

(defun my-run-python ()
  (interactive)
  (let ((default-directory (or my-python-dir-override default-directory)))
    (call-interactively #'run-python)))

Then set my-python-dir-override in your .dir-locals.el in the project root directory, and bind C-c C-p to my-run-python.

If you don't want to use .dir-locals.el, you could swap out my-python-dir-override for (projectile-project-root) (if you're a projectile user) or (project-root), though this logic will then apply to all projects.

Answer 2

Importing modules is explained in this document. For your case, in jitter.py write from . common import constants (you can use full name for common)

EDIT: The specified document treat also the case for absolute path - you may use sys.path and sys.append. Other solution(s) here, see Nagev's response or use the importlib module.