Making Money with Python

March 17th, 2012

A while back a friend told me about something called community currency, also know as Local Exchange Trading System. The basic idea of which is that people within a geographical area can exchange goods and services with bespoke unit of exchange rather that traditional cash. So, for instance, you could mow a few lawns in exchange for guitar lessons – even if it isn't the guitar teacher's lawn you are mowing. There's no physical currency as such, members of the community currency rely on volunteers to keep track of how much currency they own. I think this is a marvellous idea. It promotes healthy exchanges without the need to muddy things with something as vulgar as cash. But what struck me after a bit of research is how the whole system is in dire need of mechanisation! There's no centralised place to view your ‘account’ or way to do transactions online, and I figured there should be. So that has been my hobby project for the last few months, I've been building such a site which has recently come together to a point where I'd like to gauge how much interest is out there. I haven't even come up with a name yet, so I've been calling it by the rather uninspired moniker of ‘Currency Site’.

Apologies for the misleading title of this post. I am without shame.

Users of Currency Site can create a currency which they can use to keep track of any kind of debt. The currency creator (or provider) sets the policy on how new money is created and managed. Once created, money can be sent to other users (directly to a username or indirectly via an email address), and users can mange their funds by creating various accounts. Once funds have been sent to a user, the provider has no more control, as any user is free to store their funds or send them to others. For all intents and purposes, Currency Site is like online banking, although with a far nicer user interface than any online banking system I have ever used (which tend to be a usability minefield). Users are also able to see how much money has been minted and how much is currently in circulation (i.e. not stored by the provider), which helps to maintain trust in the system.

You may be thinking this sounds familiar if you have ever come across the Bitcoin project, but there are a few significant differences. The biggest difference is that Currency Site still requires trust in the individual or organisation that is managing the currency (i.e. the provider), and there is no enforced scarcity of new currency; providers can mint new money as they see fit. There is a little overlap, but the use cases for Currency Site are potentially broader (albeit limited in scale) compared to Bitcoin. Community currency projects are what I had in mind when working on this, but it is equally applicable for a variety of other uses. For example, lets say a family (we'll call them the the Smiths) have a few kids that don't like doing their chores, so the parents create a currency called ‘Smith Dollars’. When little Bobby Smith does his homework or cleans up his room, his parents send him 10 Smith Dollars. When Bobby has 100 Smith Dollars, he can cash them in for a new video game or spend 15 to stay up an extra hour. But if he wanted to, he could also send his sister 5 Smith Dollars in return for a loan of her laptop. Other uses could be employees keeping track of who goes for the doughnuts or a couple exchanging favours (use your imagination for that one).

Currency Site is built with Django and I've used the excellent Bootstrap library for the theme. The site is usable at the moment, but there are still a few things I want to do to it before I push it live anywhere. Just to prove it's not vaporware, here are a few screenshots:

Screenshot of currency site

Screenshot 1

Screenshot of currency site

Screenshot 2

Screenshot of currency site

Screenshot 3

I will be looking for a few brave souls to help me test this. I plan to do a private beta where the database will be completely wiped before it goes live for a while. This will give me the opportunity to really iron out the kinks, without having to worry about making a mess of the DB. If you are interested in helping out please get in touch, or +1 this if you are reading on Google+. I'd also be interested in suggestions for a good name for this project! It seems that any domain with any kind of reference to money or currency is taken (not surprising I suppose).


Rose Chafer

June 2nd, 2011
Nobel Chafer Beetle

Rose Chafer Beetle

This little guy found his way in to my flat, giving me an excellent opportunity to do a little macro photography.

Correction: I was mistaken, this is a Rose Chafer and not a Noble Chafer.

After a google images search, I've concluded it is a Noble Chafer Rose Chafer beetle. Turns out they are endangered. Shame, they are beautiful animals – if you like bugs and things like I do.

More on my Flicker photostream.


Django job at Net Communities

May 9th, 2011

Net Communities are looking for a Python/Django developer to work on an in-house project. It's a contract that would require some on-site work, but they would also consider a full-time developer for the right individual.

If you are interested, get in touch with Andy Evans.


Creating a Virtual Filesystem with Python (and why you need one)

March 20th, 2011

If you are writing an application of any size, it will most likely require a number of files to run – files which could be stored in a variety of possible locations. Furthermore, you will probably want to be able to change the location of those files when debugging and testing. You may even want to store those files somewhere other than the user's hard drive.

Any engineer worth his salt will recognise that the file locations should be stored in some kind of configuration file and the code to read the files in question should be factored out so that it isn't just scattered at points where data is read or written. In this post I'll present a way of doing just that by creating a virtual filesystem with PyFilesystem.

You'll need the most recent version of PyFilesystem from SVN to run this code.

We're going to create a virtual filesystem for a fictitious application that requires per-application and per-user resources, as well as a location for cache and log files. I'll also demonstrate how to mount files located on a web server. Here's the code:

from fs.opener import fsopendir
app_fs = fsopendir('mount://fs.ini', create_dir=True)

That's, all there is to it; two lines of code (one if you don't count the import). Obviously there is quite a bit going on under the hood here, which I'll explain below, but lets see what this code gives you…

The app_fs object is an interface to a single filesystem that contains all the file locations our application will use. For example, the path /user/app.ini references a per-user file, whereas /resources/logo.png references a per application file. The actual physical location of the data is irrelevant because as far as your application is concerned the paths never change. This abstraction is useful because the real path for such files varies according to the platform the code is running on; Windows, Mac and Linux all have different conventions, and if you put your files in the wrong place, your app will likely break on one platform or another.

Here's how a per-user configuration file might be opened:

from ConfigParser import ConfigParser
# The 'safeopen' method works like 'open', but will return an
# empty file-like object if the path does not exist
with app_fs.safeopen('/user/app.ini') as ini_file:
    cfg = ConfigParser()
    # ... do something with cfg

The files in our virtual filesystem don't even have to reside on the local filesystem. For instance, /live/ may actually reference a location on the web, where the version of the current release and a short ‘message of the day’ is stored.

Here's how the version number and MOTD might be read:

def get_application_version():
    """Get the version number of the most up to date version of the application,
    as a tuple of three integers"""
    with app_fs.safeopen('live/version.txt') as version_file:
        version_text =
    if not version_text:
        # Empty file or unable to read
        return None
    return tuple(int(v) for v in version_text.split('.', 3))

def get_motd():
    """Get a welcome message"""
    with app_fs.safeopen("live/motd.txt") as motd_file:

You'll notice that even though the actual data is retrieved over HTTP (the files are located here and here), the code would be no different if the files were stored locally.

So how is all this behaviour created from a single line of code? The line fsopendir("mount://fs.ini", create_dir=True) opens a MountFS from the information contained within an INI file (create_dir=True will create specified directories if they don't exist). Here's an example of an INI file that could be used during development:


The INI file is used to construct a MountFS, where the keys in the [fs] section are the top level directory names and the values are the real locations of the files. In above example, /user/ maps on to a directory called user relative to the current directory – but it could be changed to an absolute path or to a location on a server (e.g. FTP, SFTP, HTTP, DAV), or even to a directory within a zip file.

You can change the section to use in a mount opener by specifying it after a # symbol, i.e. mount://fs.ini#mysection

There are a few changes to this INI file we will need to make when our application is ready for release. User data, site data, logs and cache all have canonical locations that are derived from the name of the application (and the author on Windows). PyFilesystem contains handy openers for these special locations. For example, appuser://examplesoft:myapp detects the appropriate per-user data location for an application called “myapp” developed by “examplesoft”. Ditto for the other per-application directories. e.g.:


The /live/ path is different in that it needs to point to a web server:


Of course, you don't need to use the canonical locations. For instance, let's say you want to store all your static resources in a zip file. No problem:


Or you want to keep your user data on a SFTP (Secure FTP) server:


Perhaps you don't want to preserve the cache across sessions, for security reasons. The temp opener creates files in a temp directory and deletes them on close:


Although, if you are really paranoid you can store the cache files in memory without ever writing them to disk:


Setting /user/ to mem:// is a useful way of simulating a fresh install when debugging.

I hope that covers why you might need – or at least want – a virtual file system in your application. I've glossed over some the details and other features of PyFilesystem. If you would like more information, see my previous posts, check out the documentation or join the PyFilesystem discussion group.


Ken Burns effect with Javascript and Canvas

February 26th, 2011

I recently decided to look into working with the Canvas element to prototype a game idea I had. Since the easiest way to learn a technology is to use it, I set myself the goal of implementing the Ken Burns Effect.

There are a few JS slideshow scripts that do the Ken Burns effect, but I haven't seen any implemented in Canvas.

Without further ado, here is my implementation of the effect:

Your browser doesn't support canvas! Try Chrome, Firefox or Opera

If you see the effect, above, you are probably viewing this in one of the good browsers. I think it can be made to run on IE with excanvas, although I have yet to test that.

If there is enough interest, I may open source the code and add some new features / docs. In the meantime, feel free to download the code (a JQuery plugin) or run it on your site:

Ken Burns Effect in Javascript and Canvas

There's actually not that much to it. Here is the code to kenburns.js:


    $.fn.kenburns = function(options) {

        var $canvas = $(this);
        var ctx = this[0].getContext('2d');
        var start_time = null;
        var width = $canvas.width();
        var height = $canvas.height();

        var image_paths = options.images;
        var display_time = options.display_time || 7000;
        var fade_time = Math.min(display_time / 2, options.fade_time || 1000);
        var solid_time = display_time - (fade_time * 2);
        var fade_ratio = fade_time - display_time
        var frames_per_second = options.frames_per_second || 30;
        var frame_time = (1 / frames_per_second) * 1000;
        var zoom_level = 1 / (options.zoom || 2);
        var clear_color = options.background_color || '#000000';

        var images = [];
        $(image_paths).each(function(i, image_path){
        function get_time() {
            var d = new Date();
            return d.getTime() - start_time;

        function interpolate_point(x1, y1, x2, y2, i) {
            // Finds a point between two other points
            return  {x: x1 + (x2 - x1) * i,
                     y: y1 + (y2 - y1) * i}

        function interpolate_rect(r1, r2, i) {
            // Blend one rect in to another
            var p1 = interpolate_point(r1[0], r1[1], r2[0], r2[1], i);
            var p2 = interpolate_point(r1[2], r1[3], r2[2], r2[3], i);
            return [p1.x, p1.y, p2.x, p2.y];

        function scale_rect(r, scale) {
            // Scale a rect around its center
            var w = r[2] - r[0];
            var h = r[3] - r[1];
            var cx = (r[2] + r[0]) / 2;
            var cy = (r[3] + r[1]) / 2;
            var scalew = w * scale;
            var scaleh = h * scale;
            return [cx - scalew/2,
                    cy - scaleh/2,
                    cx + scalew/2,
                    cy + scaleh/2];

        function fit(src_w, src_h, dst_w, dst_h) {
            // Finds the best-fit rect so that the destination can be covered
            var src_a = src_w / src_h;
            var dst_a = dst_w / dst_h;
            var w = src_h * dst_a;
            var h = src_h;
            if (w > src_w)
                var w = src_w;
                var h = src_w / dst_a;
            var x = (src_w - w) / 2;
            var y = (src_h - h) / 2;
            return [x, y, x+w, y+h];

        function get_image_info(image_index, load_callback) {
            // Gets information structure for a given index
            // Also loads the image asynchronously, if required
            var image_info = images[image_index];
            if (!image_info.initialized) {
                var image = new Image();
                image_info.image = image;
                image_info.loaded = false;
                image.onload = function(){
                    image_info.loaded = true;
                    var iw = image.width;
                    var ih = image.height;

                    var r1 = fit(iw, ih, width, height);;
                    var r2 = scale_rect(r1, zoom_level);

                    var align_x = Math.floor(Math.random() * 3) - 1;
                    var align_y = Math.floor(Math.random() * 3) - 1;
                    align_x /= 2;
                    align_y /= 2;

                    var x = r2[0];
                    r2[0] += x * align_x;
                    r2[2] += x * align_x;

                    var y = r2[1];
                    r2[1] += y * align_y;
                    r2[3] += y * align_y;

                    if (image_index % 2) {
                        image_info.r1 = r1;
                        image_info.r2 = r2;
                    else {
                        image_info.r1 = r2;
                        image_info.r2 = r1;

                    if(load_callback) {

                image_info.initialized = true;
                image.src = image_info.path;
            return image_info;

        function render_image(image_index, anim, fade) {
            // Renders a frame of the effect
            if (anim > 1) {
            var image_info = get_image_info(image_index);
            if (image_info.loaded) {
                var r = interpolate_rect(image_info.r1, image_info.r2, anim);
                var transparency = Math.min(1, fade);

                if (transparency > 0) {
                    ctx.globalAlpha = Math.min(1, transparency);
                    ctx.drawImage(image_info.image, r[0], r[1], r[2] - r[0], r[3] - r[1], 0, 0, width, height);

        function clear() {
            // Clear the canvas
            ctx.globalAlpha = 1;
            ctx.fillStyle = clear_color;
            ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);

        function update() {
            // Render the next frame
            var update_time = get_time();

            var top_frame = Math.floor(update_time / (display_time - fade_time));
            var frame_start_time = top_frame * (display_time - fade_time);
            var time_passed = update_time - frame_start_time;

            function wrap_index(i) {
                return (i + images.length) % images.length;

            if (time_passed < fade_time)
                var bottom_frame = top_frame - 1;
                var bottom_frame_start_time = frame_start_time - display_time + fade_time;
                var bottom_time_passed = update_time - bottom_frame_start_time;
                if (update_time < fade_time) {
                } else {
                    render_image(wrap_index(bottom_frame), bottom_time_passed / display_time, 1);

            render_image(wrap_index(top_frame), time_passed / display_time, time_passed / fade_time);

            if (options.post_render_callback) {
                options.post_render_callback($canvas, ctx);

            // Pre-load the next image in the sequence, so it has loaded
            // by the time we get to it
            var preload_image = wrap_index(top_frame + 1);

        // Pre-load the first two images then start a timer
        get_image_info(0, function(){
            get_image_info(1, function(){
                start_time = get_time();
                setInterval(update, frame_time);


})( jQuery );

Spatial Bookmarking Service goes Open Source

January 9th, 2011

Locidesktop was my coffee shop coding project of last year. I was quite pleased with the results. has been happily serving link desktops to some loyal visitors for months now – with no maintenance required on my part (a good thing because I've been busy with other projects).

Rather than let the project stagnate while I do other things, I have released it as open source with the hope that other Python/Django developers will pick it up and add new features. I had never really anticipated that anyone other than myself would see the code, so it is lacking in comments and documentations, but there are some nice features that may be of interest. For instance, there's a system to expose a REST API that factors out a lot of Python bioler-plate code and corresponding javascript code exposes the desktop functionality to the browser.

There's also a pretty powerful caching system that makes rendering a desktop blindingly fast. I may have gone overboard with that, given my traffic rates. But I guess it is best to have more capacity than you need.

If you want to look through the code or fork the project, it is available on Github:

Locidesktop code

The only thing missing from the open source version is a single-site theme I purchased from, used in a few pages such as the about & privacy urls. The desktops themselves are identical to the live site because I did those myself. You can tell because of the minimalist design reflecting my artistic abilities (minimal).

There's a README in the project that will help you get started, but other than that you may have to figure things out for yourself. It's a pretty standard Django project, although I do use Jinja templates rather than Django templates. If you have any questions, please ask them in the comments, so at least there is a central repository for issues.

For more information on Locidesktop, see my previous posts on the subject.

Update: I had to recreate the repos to remove a bunch of temp files and mercurial data. If you forked before 9am GMT, 10th Jan, you may want to get this new repos.


Sneak Preview of New Features in PyFilesystem 0.4

January 1st, 2011

There have been some pretty exciting developments in PyFilesystem since version 0.3 was released – Ryan Kelly and myself have been hard at work, and there have been a number of excellent contributions to the code base from other developers. Version 0.4 will be released some time in January, but I'd like to give you a preview of some new features before the next version lands.

Pyfilesystem is a Python module that provides a simplified common interface to many types of filesystem.

It is now possible to open any of the supported filesystems from a URL in this format, which makes it very easy to specify a filesystem (or individual file) from the command line or a config file. Here's a quick example that opens a bunch of quite different filesystems:

from fs.opener import fsopendir
projects_fs = fsopendir('/projects')
zip_fs = fsopendir('zip:///foo/bar/')
ftp_fs = fsopendir('ftp://ftp/')
sftp_fs = fsopendir('s')

If you used Pyfilesystem in your application you could trivially change where your files are physically located, or where you save generated files to.

You can also open a file directly without the need to explicitly open the filesystem it is contained within, with the fsopen function, e.g.:

from fs.opener import fsopen
print fsopen('zip:///foo/bar/!dir/somefile.txt').read()
print fsopen('').read()

fsopen is very similar to the builtin open method and will return a file-like object of some kind. In fact, if you pass in a system path it works as open would (although the exceptions will be an instance of fs.errors.FSError rather than IOError).

Because of this similarity with the builtin, fsopen could be used to shadow open, and instantly add the ability for an application to open files on mediums other than a system drive. This is all it takes:

from fs.opener import fsopen as open

FS Commands

Version 0.4 also adds a number of applications that mirror some of the standard command line apps, but extend their functionality with FS URLs. For example, fsls, functions just like the ls command, but works with any of the supported filesystems:

will@will-linux:~$ fsls .
will@will-linux:~$ fsls zip://myzip
will@will-linux:~$ fsls
will@will-linux:~$ fsls s

You can also copy and move files between filesystems with fscp and fsmv, which work in a very similar manner to their cp and mv counterparts, with a few extensions such as multi-threaded copying (great for network filesystems) and an ascii progress bar. The following example copies all the .py files in my projects directory to zip file on an ftp server, and displays an progress bar to boot.

will@will-linux:~$ fscp ~/projects/*.py zip:

Then there is the fscat command that writes a file in a filesystem to the terminal. The following example displays a python file in the zip file that we created with the previous command:

will@will-linux:~$ fscat zip:!

The other commands fsmkdir, fsrm and fstree work as you may expect.


The fsserve command adds the ability to serve any of the supported filesystems over a number of protocols. The default is to serve http – in effect creating a webserver. The following is all it takes to serve the contents of your current working directory:

will@will-linux:~$ fsserve

Now if you point your browser at you will see a web-page with the contents of your current working directory (or a index.html file if present). It's not the most bullet-proof of web servers, but handy if you quickly want to serve some files. Naturally, fsserve works with any filesystem you pass to it. You could, for instance, serve the contents of a zip file without ever explicitly unzipping it, or create an ftp to http gateway by serving an ftp filesystem. The following command creates a ftp to http gateway for

will@will-linux:~$ fsserve

You also have the option of serving a filesystem over SFTP (Secure FTP), or by RPC (Remote Procedure Call). Either of these two methods expose all the functionality of the remote filesystem, so you could run a server on one machine and create/move/copy/delete files from another machine on the network (or internet). For example, the following would serve the current working directory on localhost, port 3000:

will@will-linux:~$ fsserve -t rpc -p 3000

You can then connect to that server from another machine on the network. Assuming my local IP is the following would display the directory structure from another machine on my network:

will@will-linux:~$ fstree rpc://


Any of the filesystems can be mounted on the OS with the fsmount command, which uses FUSE on Linux or DOKAN on Windows. The advantage of this is that the filesystems exposed in Python can be used in any application, and browsed with Explorer or Nautilus. The following creates a ram drive on Linux:

will@will-linux:~$ fsmount mem:// mem

Or on Windows:

C:\> fsmount mem:// M

Get the Code

There is no documentation online for the new features as yet, but if you are a brave soul and want to experiment with any of the above commands then download the code from SVN and run python install. The command line apps all have a -h which which displays help on the various options.

Bear in mind that these commands are still somewhat experimental, and some of these commands have the capacity to delete files – so be careful. That said, I'm confident to use them for my day-to-day work.

Please see the projects page page if you want to report bugs or discuss Pyfilesystem with myself and the other developers.


Python 3 Object Oriented Programming

August 20th, 2010

Packt Publising has sent me a copy of Python 3 Object Oriented Programming to review. It's quite a hefty tome and will take me a few days to get through. In the meantime, they have a free chapter to whet your appetite.

Python 3 Object Oriented Programming

Python 3 Object Oriented Programming

I'm liking this trend of free books! Watch this space for the review…


What to do with Locidesktop?

June 30th, 2010

So what to do with It's a desktop-like website bookmarking tool – if you haven't seen it, take a quick look at this example desktop.

I built Loci Desktop a few months ago and promoted it on a few geek sites. It's been running ever since, with no maintenance from myself, happily serving up start pages to a small number of regular users. There was a buzz when I promoted it, people were largely impressed, some were indifferent, but few ended up using it regularly. So now I'm left with a quandary.

I could try and promote it. But to what end? It's not like I need a certain number of visitors to cover the hosting. I'm using the same VPS as I am for my blog, and I designed Locidesktop to be ultra-low bandwidth anyway – so it effectively costs me nothing to run.

One option would be to sell the entire site outright, as the domain and technology rights. But there is currently no way of monetizing it and I doubt anyone would be interested as a commercial venture.

I could try and license it as a b2b service. A few people have commented that it would be a useful intranet service. I'm not sure about this, but it sounds plausible.

Alternatively, I could give back to the Django community and release it as open source, which I imagine would be the popular thing to do. Money isn't my primary motivator (a close second perhaps), so I wouldn't be averse to doing this. Thing is though, it would require work on my part to document it and maintain it, and I have other open source projects I would prefer to concentrate on. But I can't deny that it would be cool to see Locidesktop sites popping up over the interwebs.

Finally, I could just leave it as is. I'm pleased with how it turned out, and I have a few loyal users. Maybe I should just be satisfied.

Any options I haven't considered? Leave a comment…


PyFilesystem 0.3 released

June 20th, 2010

I am pleased to announce a new version of PyFilesystem (0.3), which is a Python module that provides a common interface to many kinds of filesystem. Basically it provides a way of working with files and directories that is exactly the same, regardless of how and where the file information is stored. Even if you don't plan on working with anything other than the files and directories on your hard-drive, PyFilesystem can simplify your code and reduce the potential of error.

PyFilesystem is a joint effort by myself and Ryan Kelly, who has created a number of new FS implementations such as Amazon S3 support and Secure FTP, and some pretty cool features such as FUSE support and Django storage integration.

As an example of how awesome this package is, take a look at the following 6 lines of code, which creates a ramdrive:

from fs.osfs import OSFS
from fs.memoryfs import MemoryFS
from fs.expose import fuse

home_fs = OSFS('~/')
home_fs.makedir('ramdrive', allow_recreate=True)
fuse.mount(MemoryFS(), home_fs.getsyspath('ramdrive'))

If you run this, a directory called ramdrive will appear in your home folder, the contents of which are stored purely in memory.

I prepared a screencast that gives a quick demonstration of some features – because if a picture is worth a thousand words, this video must be worth fifteen thousand words a second:

PyFilesystem screencast from Will McGugan on Vimeo.

See the project page on google code for more information, including API docs. There are also a couple of blog posts that will give a some more context.

This release has reached a good level of stability and maturity. I'd like to invite as many Pythonistas as possible to check out this module and possibly contribute to the project.


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Will McGugan

My name is Will McGugan. I am an unabashed geek, an author, a hacker and a Python expert – amongst other things!

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