Jun 9

Betrand Mathieus blog article on cleaning up trailing whitespace comes in handy for me as I’ve frequently run into problems with the Python test coverage tool stumbling over trailing whitespace. It also reminded me of an emacs snippet I recently installed to detect a mix of space and tabs in my Python buffers — I do set (setq indent-tabs-mode nil) in my .emacs for python-mode, however, I still occasionally somehow manage to insert some tabs in my source buffers. So I came up with the following snippet which validates that a buffer in python-mode doesn’t contain any tabs. It’s hooked up with the very general write-file-hook, but there is no python-specific hook on saving buffers. In case the buffer does contain any tab, it will leave the point (the place where your cursor will be) at the fount tab.

; code snippet GUID 32F94179-A86B-4780-8645-8A526BD8533A
(defun no-tab-validation (buffer)
  (interactive "bValidate buffer:")
    (unless (equal (buffer-name (current-buffer)) buffer)
      (switch-to-buffer buffer))
    (if (re-search-forward "\t" nil t)
    (error "Buffer %s contains tabs" buffer))))

(defun py-tab-validate-on-save-hook ()
  (when (equal mode-name "Python")
    (no-tab-validation (buffer-name (current-buffer)))))

(add-hook 'write-file-hook 'py-tab-validate-on-save-hook)

;;; inhibit tabs in some modes
(defun set-indent-tabs-mode (value)
  "Set indent-tabs-mode to value."
  (setq indent-tabs-mode value))

(defun toggle-tabs ()
  "Toggle `indent-tabs-mode'."
   (not indent-tabs-mode)))

(defun disable-tabs-mode ()
  (set-indent-tabs-mode nil))

(add-hook 'sgml-mode-hook 'disable-tabs-mode)
(add-hook 'xml-mode-hook 'disable-tabs-mode)
(add-hook 'python-mode 'disable-tabs-mode)

Posted by Holger Schauer

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Apr 16

One of the nicer extensions of mozilla I use is It’s all text. It allows you to call an external editor to edit text fields which is a really nice thing if you’re editing longer wiki pages, for instance.

Not surprisingly, my external editor of choice is XEmacs. But my XEmacs is heavily configured and loads a lot of stuff. Even worse, I usually run a beta version with debugging turned on, so that it runs extra slow, so the time gap between clicking on that little “edit” button below the text field and the moment when I could finally start typing started to annoy me quickly.

I remembered that some years ago I used to log in remotely to a running machine, fire up some script and have either my running XEmacs session connected or a new XEmacs process started. Connecting to the running XEmacs happens via gnuclient, so much was clear but gnuclient doesn’t start a new XEmacs if there is none running (actually, the server process gnuserv will die when the XEmacs process terminates, so there isn’t much gnuclient can do). The emacs wiki page linked to above already contains a number of scripts that eventually do what I need to do, but I’ve found none of them convincing, so here is my version. It’s linux specific in its BSD style call to ‘ps’ to determine the running processes, but should be portable sh otherwise. I could have sprinkled the fetch_procs function with OS specific variants, but as I’m currently running my XEmacs on linux only, I left that as an exercise to the reader.

[geshi lang=bash]


emacs=xemacs gnuclient=gnuclient gnuserv=gnuserv user=id -un


fetch_procs () { ps xU $user }

runninggnuserv=fetch_procs | grep "[^]]$gnuserv" runningemacs=fetch_procs | grep "[^]]$emacs" if [ “$?” -eq “0” ]; then gnuservpid=echo $runninggnuserv | cut -f1 -d'' emacspid=echo $runningemacs | cut -f1 -d'' echo “Using running gnuserv $gnuservpid of emacs $emacspid” $gnuclient $gnuclientopts “$@” else echo “Starting new $emacs” $emacs “$@” fi [/geshi]

ObTitle: Panic at the disco, from the album “A fever you can’t sweat out”

Posted by Holger Schauer

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Dec 10

I’ve become a python programmer, too, lately, due to a job change. Python is a fine language so far, although to me it’s mostly just like Ruby, though with even less functional flavour. However, just as with Ruby, I’m really missing slime, the superior lisp interaction mode for Emacs, when hacking python code. I could now start to write down a list of things I’m missing (which I’ve intended to do), however, Andy Wingo spares me the hassle, as he has just written an excellent article on slime from a python programmers view.

However, I would like to elaborate a little on the main difference for me: the client/server socket approach of slime. Let me briefly recapulate what this implies: slime consists of two parts, a client written in Emacs lisp and a server written in Common Lisp (AFAIK there is at least also an implementation for clojure, maybe also one for some scheme implementation). In order to use slime in it’s full glory, it’s hence required that you have a common lisp process running which in turn runs the slime server part. If you now fire up slime, you’ll get an interaction buffer over which you can access the REPL of the lisp process, which in python would be the interpreter prompt. You can then interact with the lisp process, evaluating pieces of code from your lisp source code buffer directly in the connected lisp process. What is incredibly useful for me is that you can not only start a new lisp process but also connect to an already running lisp process, given that it has the slime server started (this is obviously mainly useful if the lisp implementation you use has multi-threading capabilities). I use it to connect to a running web server application, which I can then inspect, debug and modify. Modification includes redefinition of functions, macros and classes, which of course is also a particular highlight of Common Lisp. I would like to cite a comment of the reddit user “fionbio” he made wrt. to the linked article: In fact, Python language wasn’t designed with lisp-style interactive development in mind. In CL, you can redefine (nearly) anything you want in a running program, and it just does the right thing. In Python, there are some problems, e.g. instances aren’t updated if you modify their class. Lisp programmers often, though not always, refer to various things (functions, classes, macros, etc.) using symbols, while Python programs usually operate with direct references, so when you update parts of your program you have much higher chances that there will be a lot of references to obsolete stuff around.

To complement Bill clementsons excellent article series on slime a little, I’m going to describe how I’m using/configuring python-mode to make it match my expectations a little closer. Essentially I would like to access my python process just as I would with slime/Common Lisp, but that’s not possible. The reason, btw., is nearly unchanged: I need to code on a web server app (written in Zope) which may not even run on the same machine I’m developing on. Let’s first cover the simple stuff: To enable a reasonable command interface to the python interpreter, I require the ipython emacs library. If the python interpreter runs locally, I also use py-complete, so that I can complete my code at least a little. Unfortunately, this breaks when the python interpreter doesn’t run locally, because the py-complete needs to setup some things in the running python process, which it does by writing to a local temp file and feeding it to the python process. Unfortunately, the code in py-complete lacks customizability, i.e., you can’t specify where that temp file should be located — I should be able to come up with a small patch in the near future, which I will add below. Finally, I also require doctest-mode as a support for writing doctests, but that’s not really relevant.

Now, on to the more involved stuff: I introduce some new variables and a new function py-set-remote-python-environment, which uses the those variables to do a remote call (via ssh) to python. This at least allows me to do things like setting py-remote-python-command to “/home/schauer/zope/foo-project/bin/instance” and py-remote-python-command-args to “debug”, so that I can access a remote debug shell of my current zope product. That alone will only allow me to fire up and access the remote python, so I could now develop the code locally, having it executed remote. More typical though is that you would also want to keep the code on the remote machine, too: for this I use tramp, a package for remotely accessing files/directories from within emacs. In combination, this allows me to edit and execute the code on the remote machine. It is still nowhere near what is possible with slime, but at least it allows me to persue my habit of incremental and interactive development from within my usual emacs installation (i.e., it doesn’t require me to deal with any Emacs related hassle on the remote machine).

;;; python-stuff.el --- python specific configuration

(when (locate-library "ipython")
  (require 'ipython))

(when (locate-library "doctest-mode")
  (require 'doctest-mode))

(defvar py-remote-connect-command "ssh""*Command for connecting to a remote python, typically \"ssh\"")
(defvar py-remote-connection-args '("user@remotemachine")"*List of strings of connection options.")
(defvar py-remote-python-command "python""*Command to execute for python")
(defvar py-remote-python-command-args '("-i")"*List of strings arguments to be passed to `py-remote-python-command`.")
(defvar py-remote-python-used nil"Remember if remote python is used.")

(defun py-set-remote-python-environment ()
  (let ((command-args (append py-remote-connection-args 
                  (list py-remote-python-command)
    (setq py-python-command py-remote-connect-command)
    (setq py-python-command-args command-args))
  (setq py-remote-python-used t))

(when (locate-library "py-complete")
  (autoload 'py-complete-init "py-complete")
  (defun my-py-complete-init ()"Init py-complete only if we're not using remote python"
    (if (not py-remote-python-used)
  (add-hook 'python-mode-hook 'my-py-complete-init))

Posted by Holger Schauer

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