RYAN MCGUIRE

Audacious Dynamic Playlist powered by inotify

I was playing around with StreamRipper today to record a shoutcast stream I enjoy, and I thought to myself: wouldn't it be nice to be able to continuously play all the files I've downloaded without having to manually queue the new files in Audacious?

So, I scratched an itch. With a little DBUS, pyinotify, and an optparse wrapper, I now have a tool to automatically add the tracks to my Audacious playlist. You can grab the latest version on github.

Streamripper does have a relay option (-r) to allow you to listen to the same stream as you're ripping it, and if that's what you want, the following script is superfluous. However, what I wanted was something slightly different: I didn't necessarily want to just listen to the stream live, instead, I wanted the ability to jump around between the tracks already downloaded, exploring different songs, but with the list of tracks ever expanding. That's what this script allows.

You'll need python-dbus and setuptools installed, then just install with:

easy_install http://github.com/EnigmaCurry/audacious-plugins/zipball/master

Startup StreamRipper with your favorite audio stream and point the tool at your target directory:

python -m ec_audacious.dynamic_filesystem_playlist /path/to/your/streamripper_location

Now when StreamRipper creates a new file, it will get automatically (instantaeneously actually, thanks to inotify!) to your Audacious playlist.

Alternatively, you can use the streamripper wrapper script that I've included to start both the filesystem monitor as well as streamripper in one go:

Put the following in your .bashrc file or somewhere equivalent:

alias streamripper="python -m ec_audacious.streamripper"

Then whenever you run streamripper, you'll actually be running the wrapper script instead:

streamripper http://your-cool-stream.com:8000 --audacious

By aliasing streamripper to point to the ec_audacious.streamripper wrapper script, we're effectively adding a new option to streamripper called --audacious which spawns our filesystem monitor.

Writing an OpenOffice.org Calc extension in Python

A very well organized group of thugs steals my money every day. I'm getting really tired of it, but I found a way to save at least some of my money so they don't steal nearly as much of it, nearly as often. For whatever reason, this gang hasn't devised a way to steal gold and silver nearly as efficiently as these little green pieces of paper that they call money. So I buy gold and silver whenever I can as a hedge against 'inflation' (which is really just their gang-speak for the wholesale-theft of my money.)

I want to keep track of how much gold and silver I've bought, when I bought it, and inevitably I'll still want to know how many green pieces of paper I could theoretically trade it all in for.

The easiest way to track all this information was to create a spreadsheet in OpenOffice.org's Calc. I created a sheet for gold purchases and another sheet for silver purchases. Everytime I make a purchase, I record the number of ounces, what form it is in (coins, bars, junk etc), who I bought it from, when I bought it, and the price I paid in FRNs (Federal Reserve Notes, aka green pieces of paper.) On another sheet I total the number of ounces I own and multiply it by the current spot price for the metal, which gives me the current price I could get if I sold it for FRNs. When tallying this total, I reference a special cell on the sheet, one that has the current spot price for gold, and another for silver.

But checking the spot price myself and manually updating those cells was just too tedious for my programmer's heart. I wanted OpenOffice.org to automatically retrieve this information for me. So, I started researching OpenOffice.org extensions (plugins).

Turns out, OpenOffice.org extensions can be written in my favorite programming language, Python (yea!), so I wrote the following extension a few weekends ago. It's on github and can be downloaded with git:

  git clone git://github.com/EnigmaCurry/SpotMetal.git

If you just want the pre-compiled extension, it can be downloaded here locally:

SpotMetal-0.1.oxt

You install it inside OpenOffice.org by going to Tools -> Extension Manager and clicking on Add and browsing to the SpotMetal-0.1.oxt file you downloaded or built yourself.

Once you have it installed, you now have a new Calc function available called SPOTMETAL which takes two arguments:

• metal - Which metal you want to look up. Can be one of "gold", "silver", "platinum", or "palladium"
• bidAsk - Whether you want the bid or the ask price. Can be either "bid" or "ask".

The price will automatically be refreshed every 5 minutes by default, but you can also force a refresh with the Calc function called SPOTMETALREFRESH.

Here's an example OpenOffice.org spreadhseet that shows how you might track your own precious metal investment portfolio. The big button labeled "Refresh Spot Price" does what it says it does, but requires a bit more boiler-plate code in order for it to actually display on screen. In OpenOffice.org, you can see another macro called doReCalculate:

• Tools->Macros->Organize Macros->OpenOffice.org Basic
• MetalTrackerExample.ods->Standard->SpotMetal->doReCalculate.

This extra macro is necessary to actually force the spreadsheet to request new data from the extension when you click the "Refresh Spot Price" button.

While this extension might be of use to you if you also invest in precious metals, I guess the main reason I posted this is because it took a good deal of time researching how to write a Python extension for OpenOffice.org. Check out the source code on github if you're looking to write your own extension, it's got it's own Makefile and hopefully it's documented well enough for it be useful for someone in the future.

Distributing Jython Apps in a Single JAR file

I've been writing a lot of one-off type applications at work lately, which is always kind of a joy for me because these sorts of applications don't need to be maintained or supported in any way, which means I can write them however I want.

So I write them in Python :)

Jython allows me to interface with all the plethora of Java libraries that we use at work, and it lets me program in a language that not only I can tolerate, but one that I respect and love.

But even though these are one-off applications, they still need to be easy to use, and in some cases I won't even be the one running the application. I want these applications to just work damnit.

So, packaging my Jython application into a single executable jar file that contains all of the third party dependancies inside is my goal. I want to send the user the jar file, have them double click on it, and have it immediately start running. It can't get a whole lot easier than that.

The Jython wiki has a page about doing something along these lines. The recipe there called the Jar Method works quite well. The one drawback that it has is that all of the Java dependancies need to be exploded into the main jar root, which when you're dealing with dozens of jar dependancies, it can start to get tedious, messy, and in some cases will even violate the license of a particular library.

One-Jar is a special class loader that can load a jar file that is inside of another jar file, something that the regular class loader from Sun is incapable of doing. Using One-Jar lets my application reside inside of a jar file and contain all my dependancies as seperate jar files inside the main jar file.

I've created a sample project that shows how I normally create a new Jython project hosted inside a single jar file with One-Jar. You'll need the following tools to check out the project:

• A Java SDK (tested with OpenJDK 1.6)
• Apache Ant (tested with version 1.7)
• Git (to checkout the project)

Check out the project like so:

 git clone git://github.com/EnigmaCurry/Single-JAR-Jython-Example.git

Build the project:

cd single-jar-jython-example

ant

Run the example by double clicking it or via the command line:

 java -jar JythonExcelExample.jar

This is just a demonstration app, it doesn't do a whole lot, it outputs an excel file in the current directory listing some computer parts. The point of the application is to show how Jython can integrate with existing Java third-party libraries (in this case Apache POI.)

Instructions for basing your own application on this example are contained inside the README.txt file.

Jython Shell Server -- Adding a REPL to any Java app

I love programming in Python. I get paid to write Java though. Due to Java's verboseness, and lack of a REPL, this can be very frustrating for me.

In Python, the usual way I explore a new library or mock up a new idea is to immediately start coding in Python's interactive interpreter (or REPL). This is often times more efficient than reading (let alone finding) the documentation for the library. I can quickly see if something is going to work before I code inside my larger application.

Java doesn't have an interactive interpreter.. but Jython does! However, setting up Jython, especially interfacing with an already large Java application, can be difficult. One such difficult situation I deal with at work is in Weblogic. With Weblogic, I deploy my application directly to a running Weblogic server, and I never get to see a console in this process, so how am I ever going to run a Jython interactive interpreter?

This morning I got bored and wrote up a quick solution: JythonShellServer. JythonShellServer embeds into any Java application and starts a Telnet server that serves up Jython interactive shells. You can push any Java object that you want to manipulate into Jython's local environment. Run "telnet localhost 7000" and you can use Python code to explore your entire application's running environment.

JythonShellServer works, but I only just wrote it this morning, so consider it alpha quality at the moment. Check out the project page on github.

AutoComplete.el : Python Code Completion in Emacs

A friend of mine and I like to show off to each other little Emacs tips and tricks we learn. Today, he introduced to me the very cool AutoComplete.el package. AutoComplete.el is intriguing to me because, unlike ropemacs mode which I've blogged about before, the completions AutoComplete.el provides are inline with your code in a dropdown box instead of in a seperate window (windows in Emacs are what most people call frames). However, AutoComplete is only a completion framework, it doesn't know anything about Python. Instead, it allows the user to plug into it, feeding it whatever sorts of intelligent completion you want, including Rope.

Setup

The two most important completions I want to integrate into it are Rope and yasnippet. AutoComplete can handle both of them nicely. You'll need to install the very latest development version (as of December '08) of Rope, Ropemacs and Ropemode:

sudo apt-get install mercurial
mkdir /tmp/rope && cd /tmp/rope
hg clone http://bitbucket.org/agr/rope
hg clone http://bitbucket.org/agr/ropemacs
hg clone http://bitbucket.org/agr/ropemode
sudo easy_install rope
ln -s ../ropemode/ropemode ropemacs/
sudo easy_install ropemacs

You'll also need to install Pymacs and Yasnippet if you haven't already:

mkdir -p ~/.emacs.d/vendor && cd ~/.emacs.d/vendor
wget http://pymacs.progiciels-bpi.ca/archives/Pymacs-0.23.tar.gz
tar xfv Pymacs-0.23.tar.gz
cd Pymacs-0.23
make
sudo easy_install .
cd ~/.emacs.d/vendor
wget http://yasnippet.googlecode.com/files/yasnippet-0.5.9.tar.bz2
tar xfv yasnippet-0.5.9.tar.bz2
cd ~/.emacs.d
ln -s vendor/yasnippet-0.5.9/snippets/ .

Make sure Pymacs and Yasnippet get into your load path, in your .emacs:

(add-to-list 'load-path "~/.emacs.d/vendor")
(progn (cd "~/.emacs.d/vendor")
       (normal-top-level-add-subdirs-to-load-path))

Install AutoComplete.el 0.1.0 (0.2.0 is now out, and is not compatible with this post, I'll try and update later):

cd ~/.emacs.d/vendor
wget http://www.emacswiki.org/emacs/?action=browse;id=auto-complete.el;raw=1;revision=5

Now to add some more elisp to your .emacs somewhere:

(require 'python)
(require 'auto-complete)
(require 'yasnippet)

(autoload 'python-mode "python-mode" "Python Mode." t)
(add-to-list 'auto-mode-alist '("\\.py\\'" . python-mode))
(add-to-list 'interpreter-mode-alist '("python" . python-mode))

;; Initialize Pymacs                                                                                           
(autoload 'pymacs-apply "pymacs")
(autoload 'pymacs-call "pymacs")
(autoload 'pymacs-eval "pymacs" nil t)
(autoload 'pymacs-exec "pymacs" nil t)
(autoload 'pymacs-load "pymacs" nil t)
;; Initialize Rope                                                                                             
(pymacs-load "ropemacs" "rope-")
(setq ropemacs-enable-autoimport t)

;; Initialize Yasnippet                                                                                        
;Don't map TAB to yasnippet                                                                                    
;In fact, set it to something we'll never use because                                                          
;we'll only ever trigger it indirectly.                                                                        
(setq yas/trigger-key (kbd "C-c <kp-multiply>"))
(yas/initialize)
(yas/load-directory "~/.emacs.d/snippets")



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;                                         
;;; Auto-completion                                                                                            
;;;  Integrates:                                                                                               
;;;   1) Rope                                                                                                  
;;;   2) Yasnippet                                                                                             
;;;   all with AutoComplete.el                                                                                 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;                                         
(defun prefix-list-elements (list prefix)
  (let (value)
    (nreverse
     (dolist (element list value)
      (setq value (cons (format "%s%s" prefix element) value))))))
(defvar ac-source-rope
  '((candidates
     . (lambda ()
         (prefix-list-elements (rope-completions) ac-target))))
  "Source for Rope")
(defun ac-python-find ()
  "Python `ac-find-function'."
  (require 'thingatpt)
  (let ((symbol (car-safe (bounds-of-thing-at-point 'symbol))))
    (if (null symbol)
        (if (string= "." (buffer-substring (- (point) 1) (point)))
            (point)
          nil)
      symbol)))
(defun ac-python-candidate ()
  "Python `ac-candidates-function'"
  (let (candidates)
    (dolist (source ac-sources)
      (if (symbolp source)
          (setq source (symbol-value source)))
      (let* ((ac-limit (or (cdr-safe (assq 'limit source)) ac-limit))
             (requires (cdr-safe (assq 'requires source)))
             cand)
        (if (or (null requires)
                (>= (length ac-target) requires))
            (setq cand
                  (delq nil
                        (mapcar (lambda (candidate)
                                  (propertize candidate 'source source))
                                (funcall (cdr (assq 'candidates source)))))))
        (if (and (> ac-limit 1)
                 (> (length cand) ac-limit))
            (setcdr (nthcdr (1- ac-limit) cand) nil))
        (setq candidates (append candidates cand))))
    (delete-dups candidates)))
(add-hook 'python-mode-hook
          (lambda ()
                 (auto-complete-mode 1)
                 (set (make-local-variable 'ac-sources)
                      (append ac-sources '(ac-source-rope) '(ac-source-yasnippet)))
                 (set (make-local-variable 'ac-find-function) 'ac-python-find)
                 (set (make-local-variable 'ac-candidate-function) 'ac-python-candidate)
                 (set (make-local-variable 'ac-auto-start) nil)))

;;Ryan's python specific tab completion                                                                        
(defun ryan-python-tab ()
  ; Try the following:                                                                                         
  ; 1) Do a yasnippet expansion                                                                                
  ; 2) Do a Rope code completion                                                                               
  ; 3) Do an indent                                                                                            
  (interactive)
  (if (eql (ac-start) 0)
      (indent-for-tab-command)))

(defadvice ac-start (before advice-turn-on-auto-start activate)
  (set (make-local-variable 'ac-auto-start) t))
(defadvice ac-cleanup (after advice-turn-off-auto-start activate)
  (set (make-local-variable 'ac-auto-start) nil))

(define-key python-mode-map "\t" 'ryan-python-tab)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;                                         
;;; End Auto Completion                                                                                        
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

Github

These changes are also applied to my Emacs environment on Github. I'm continuously trying to improve my emacs setup, so if you're reading this a few months/years after this post was made, you may want to check there for improvements.

Update Jan 30 2009: I made some modifications to the tab complete order, a regular indent is applied first before autocompletion. Autocompletion is also not applied unless you are at the end of a word. This is useful when you press Tab at the beginning of a line to indent/outdent.

Usage

Once you got everything setup, usage is real easy:

1. Open up a python (.py) file
2. Press TAB when you want to use code completion or to insert a snippet.

The first time you attempt to use code completion you'll be prompted to enter the root of your project directory.

Future

It wasn't too long ago when Python code completion inside Emacs was just a pipedream. So now that we have it, let's make some more pipedreams: I'd like to popup some nice contextual help for method arguments as well as python documentation for the current method/class being completed.

The possibilities are pretty much endless. I love Emacs.