Using TAB key for indentation in Python REPL produces strange indentation problems

Question

I'm using the Python REPL in a comint window via the run-python command, and I'm seeing bad behavior when I use the TAB key to do my indentation. For example:

>>> for i in range(3):
...     print(i)
  File "<stdin>", line 2
    print(i)
        ^
IndentationError: expected an indented block

Here, the indentation before print was created using TAB. I use TAB when editing normal Python buffers, and it inserts 4 spaces in those cases. Here it seems to be inserting an actual TAB and it results in an IndentationError.

I'd like it if TAB would just insert 4 spaces. I'm sure this is something really simple, but it's eluding me. Anyone know what I'm doing wrong?

This does not reproduce for me. Does it reproduce for you in emacs -Q? — PythonNut
– PythonNut, Commented Feb 10, 2015 at 19:43
No, it doesn't reproduce with -Q. I'm sure (as you've confirmed) that it's something in my config, but I'm too brain-tired right now to make an effective stab at tracking down the right setting. I guess a more concrete question is: What variable - if any - controls what TAB does in the REPL? — abingham
– abingham, Commented Feb 10, 2015 at 20:02
I see... What does C-h k TAB say? It should lead you to python-shell-completion-complete-or-indent. That, in turn calls indent-for-tab-command, which is part of the regular emacs indentation code. — PythonNut
– PythonNut, Commented Feb 10, 2015 at 20:06
C-h k TAB is actually bound to yas-expand. However, if I run either python-shell-completion-complete-or-indent or indent-for-tab-command directly to insert the indentation, I still get the odd behavior. — abingham
– abingham, Commented Feb 10, 2015 at 21:08
Try M-: (setq tab-width 4 indent-tabs-mode nil) RET in the python buffer. — PythonNut
– PythonNut, Commented Feb 10, 2015 at 21:13

PythonNut · Accepted Answer · 2015-02-11 18:18:10Z

1

Hm... Let me make this an answer.

TAB in a Python REPL triggers yas-expand in your case. This in turn calls python-shell-completion-complete-or-indent, which calls indent-for-tab-command. This is controlled by the regular Emacs indentation variables, which are buffer local. To fix this, you can do the following:

(add-hook 'inferior-python-mode-hook
  (lambda ()
    (setq
      indent-tabs-mode nil ;; i.e. indent with spaces
      tab-width 4          ;; i.e. tabs consts of 4 spaces
      )))

answered Feb 11, 2015 at 18:18

PythonNut

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I was wondering if you'd answer ;) That's exactly the hook I created as well.

abingham
– abingham

2015-02-12 05:28:43 +00:00
Commented Feb 12, 2015 at 5:28

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