Python mode in Emacs: No such file or directory, pdb

Question

I have a python script that I want to debug with python-mode. I read in this thread that I can debug my python script with M-x pdb, however I get the following

Answer 1

Everyone is going wild saying you gotta make a pdb file and make it an executable and then type ./pdb your_code.py. It is easier than that.

Be where you want to run the debugger from. Probably in your python file, maybe use M-x cd to get somewhere.

Then type: M-x pdb

It will prompt you with:

Run pdb (like this):

You want to make that look like:

Run pdb (like this): python -m pdb your_code.py

Sometimes if I want to run my code as a module.

Run pdb (like this): python -m pdb -m some_package.my_code

Then type help and go read this https://docs.python.org/3/library/pdb.html

Answer 2

At a shell prompt type

which pdb

In Emacs, type M-x customize. Select Programming > Tools > Gud. Set the value of gud-pdb-command-name to the path returned by which pdb.

If your version of Emacs presents a different organization for the customize menu, you could also try

C-h v gud-pdb-command-name

Then click on the customize link, and set the path to pdb there.

Though the instructions above are different, I found this out by reading "Running pdb under emacs" .

Answer 3

You can create a custom command like this:

;; PDB command line
(defun user-python-debug-buffer ()
  "Run python debugger on current buffer."
  (interactive)
  (setq command (format "python -u -m pdb %s " (file-name-nondirectory buffer-file-name)))
  (let ((command-with-args (read-string "Debug command: " command nil nil nil)))
    (pdb command-with-args)))

Answer 4

In Emacs 23.3.1 and presumably higher, yet another variation is to use the Emacs shell, Eshell (M-x eshell). Under Eshell, there's a pre-existing, Lisp-based definition of pdb. These Lisp functions work in Eshell just like ordinary shell commands.

So pdb "./manage.py runserver" will start a Django server, for instance.

Answer 5

To run the Python Debugger, M-x pdb expects to find an executable named pdb. While the pdb executable may exist in some Python distributions, it doesn't exist in all of them.

A proposal to fix this is in GNU bug report #21521: pdb default suggested command.

Until the bug is fixed, you can set the variable gud-pdb-command-name to define the command used to launch pdb. In .emacs, add...

(setq gud-pdb-command-name "python -m pdb")

Answer 6

Further to my comment earlier, and your subsequent update to the question:

First figure out a value for $PATH that works in your terminal. Use which pdb to find where the pdb executable is located.

Then, set the $PATH environment variable explicitly in Emacs, and sync it to exec-path as follows:

(setenv "PATH" "/usr/local/bin:/usr/bin:/bin:/some/other/dir")
(setq exec-path (split-string (getenv "PATH") path-separator))

It's possible you would need to also explicitly set PYTHONPATH or similar environment variables; you can do that using lines like the "setenv" line above, or just use the exec-path-from-shell elisp package.

Update

Okay, so it turns out Emacs' pdb command isn't provided by python-mode, and it expects to find an executable called "pdb". The easy way to fix this, then is to create a shell wrapper called "pdb", in a directory on your $PATH:

#!/bin/sh
exec python -m pdb "$@"

(I found a note here suggesting this technique.)

The equivalent under Windows would be a file called pdb.bat, containing:

python -u -m pdb %1

(The -u prevents Python from buffering its output.)