Mac OS X: new user tips

Over the couple of weeks I've been using an Apple iMac, and as a Windows/Linux user I've found navigating the desktop has been something of a learning experience for me.

As different as they are, in many ways the standard Windows and Linux desktops are idiomatically quite similar these days, and both support the standard PC three-button mouse. By contrast the Mac OS X desktop environment (and its use of the infamous one-button mouse) has a number of differences which can turn even basic operations (for example, cut-and-paste) initially into something of a challenge.

However some basic knowledge should go a long way in helping. First, there are the three essential keys you need to know about:

• Command key: [⌘]
• Option key: [⌥]
• Control key: [ctrl]

(The links give more background but aren't essential to the following. You can think of the option key as being the same as the "Alt" key on Windows/Linux.)

Then:

• Emulating the right-hand mouse button: [ctrl] + mouse click (essential for desktop and web applications that use this to activate context menus and so on)

Basic text editing operations:

• Cut: [⌘] + [x]
• Copy: [⌘] + [x]
• Paste: [⌘] + [x]

Basic keys for navigating within text documents:

• Home: [↖]
• End: [↘]
• Page up: [⇞]
  
• Page down: [⇟]
  

Useful shortcuts for navigating the desktop:

• Cycle between open windows: [⌥] + [tab]
• Zoom out (pulls back to show all open windows): [F9]
• Show desktop (hides all open windows): [F11]
  

And finally (and essential if you're programming and find your Apple keyboard is missing a hash key):

• Hash symbol ("#"): [⌥] + [3]
  

These all work on OS X 10.4.11 ("Tiger"), which is admittedly no longer a very recent release, but hopefully they're also applicable to later Mac OSes. I can't say that I've fallen in love with Apple as a result, but they have enabled me to operate at an acceptably functional level (until I can get my Linux workstation up and running!).

Managing Python packages: virtualenv, pip and yolk

I've recently been playing with the Python virtualenv package - along with pip and yolk - as a way of managing third-party packages. This post is my brief introduction to the basics of these three tools.

virtualenv lets you create isolated self-contained "virtual environments" which are separate from the system Python. You can then install and manage the specific Python packages that you need for a particular application - safe from potential problems due to version incompatibilities, and without needing superuser privileges - using the pip package installer. yolk provides an extra utility to keep track of what's installed.

1. virtualenv: building virtual Python environments

virtualenv can either be installed via your system's package manager (for example, synaptic on Ubuntu), or by using the easy_install tool, i.e.:

$ easy_install virtualenv

(If you don't have the SetupTools package which provides easy_install then you can download the "bootstrap" install script from http://peak.telecommunity.com/dist/ez_setup.py. Save as ez_setup.py and run using /path/to/python ez_setup.py.)

Once virtualenv is installed you can create a new virtual environment (called in this example, "myenv") as follows:

$ virtualenv --no-site-packages myenv

This makes a new directory myenv in the current directory (which will contain bin, include and lib subdirectories) based on the system version of Python. The --no-site-packages option tells virtualenv not to include any third-party packages which might have been installed into the system Python (see the virtualenv documentation for details of other options).

To start using the new environment, run the environment's "activate" command e.g.:

$ source myenv/bin/activate

The shell command prompt will change from e.g. $ to (myenv)$, indicating that the "myenv" environment (and any packages installed in it) will be used instead of the system Python for applications run in this shell. (Note that the Python application code doesn't need to be inside the virtual environment directory; in fact this directory is just using for the packages associated with the virtual environment.)

Finally, when you've finished working with the virtual environment you can leave it by running the deactivate command (also in the bin directory).

(On Windows you may have to specify the full path to the "Scripts" directory of your Python installation when invoking the easy_install and virtualenv commands above, e.g. C:\Python27\Scripts\virtualenv. Also, note that when a virtual environment is created it won't contain a "bin" directory - instead it's activated by invoking the Scripts\activate batch file in the virtual environment directory. Invoking the deactivate command exits the environment as before.)

2. pip: installing Python packages

Once you're created a virtual environment you can start to add packages (which is really the point of doing this in the first place). virtualenv automatically includes both easy_install and an alternative package installer called pip (at least, for virtualenv 1.4.1 and up; earlier versions only have easy_install, so you'll need to run easy_install pip within the virtual environment in order to get it).

Most packages that are easy_installable can also be installed using pip, and it's designed to work well with virtualenv. However I think its main advantage is that it offers some useful functionality that's missing from easy_install - most significantly, the ability to uninstall previously installed packages. (Other useful features include the ability to explicitly control and export versions of third-party package dependencies via "requirements files" - see the pip documentation for more details.)

Basic pip usage looks like this:

(myenv)$ pip install python-dateutil # install latest version of a package

(myenv)$ pip uninstall python-dateutil # remove package

(myenv)$ pip install python-dateutil==1.5 # install specific version

(As an aside, the python-dateutil package is illustrative of one of the advantages of using pip over easy_install: after installing the latest version of python-dateutil, I discovered that it's only compatible with Python 3 - an earlier 1.* version is required to work with Python 2. pip let me uninstall the newer version and reinstall the older one.)

3. yolk: checking Python packages installed on your system

The final utility I'd recommend is yolk, which provides a way of querying which packages (and versions) have been installed in the current environment. It also has options to query PyPI (the Python Package Index). Installing it is easy:

(myenv)$ pip install yolk

Running it with the -l option (for "list") then shows us what packages are available:

(myenv)$ yolk -l
Python          - 2.6.4        - active development (/usr/lib/python2.6/lib-dynload)
pip             - 1.0          - active
python-dateutil - 1.5          - active
setuptools      - 0.6c9        - active
wsgiref         - 0.1.2        - active development (/usr/lib/python2.6)
yolk            - 0.4.1        - active

(See the yolk documentation to learn more about its other features.)

Summary

Obviously the above is just an introduction to the basics of virtualenv, pip and yolk for managing and working with third-party packages - but hopefully it's enough to get started. If you're interested in using virtualenv in practice then Doug Hellman's article about working with multiple virtual environments (and his virtualenvwrapper project, which provides tools to help) is recommended as a starting point for further reading.

Richard Stallman: "A Free Digital Society?"

About a month ago I was fortunate to attend an IET-hosted lecture by Richard Stallman, entitled "A Free Digital Society?". Probably most famous as the originator of the GNU project (out of which came GNU/Linux) and initiator of the free software movement, Stallman has for many years been an active and vocal advocate for free software, and has a campaigned against excessive extension of copyright laws

He began the talk with the observation that there is an implicit assumption in the recent movement towards "digital inclusion", that using computers and the internet is inherently good and beneficial. However, as the question mark in the title of his talk indicated this assumption merits closer attention, as (in his opinion) there are various issues and threats associated with these technologies. These include:

• Survelliance: technology now makes it possible for ISPs, websites and other organisations to monitor and analyse what individuals do online (e.g. the sites that they visit, things they buy, search terms they use etc) to an extent to which (in Stallman's words) "Stalin could only dream".

• Censorship: for example, governments or corporations blocking access to particular websites (think Google in China), or even forcing them to close.

• Restrictions on users imposed by data formats: both proprietary (e.g. Silverlight) and patented data formats (e.g. MP3) restrict what the end user is able to do with the data they encode.

• Non-free software: here "free" is in the sense of "freedom", rather than price. Non-free software is essentially software that isn't under the control of you, the user - in the case of proprietary software, it's controlled by the owner (for example Microsoft, Apple, Amazon) who is able to insert features (e.g. to track user behaviour) that serves their interests rather than those of the user. By contrast, free software - which by the way you can still charge money for - gives the user four basic freedoms: 0. to run the software for any purpose; 1. to study how the software works, and make changes to it; 2. to redistribute the software as-is; 3. to redistribute the software with your changes (see the free software definition). In this way malicious features can be detected and removed, and control is returned to the user.
  

• "Software as a service" (SaaS): in Stallman's definition, "software as a service" is anything where the computation is done by programs that you can't control - this is like non-free software above, because someone else has control and can change how your computing is done at any time without your permission. He made a distinction between things like e-commerce, online storage storage (e.g. Dropbox), publishing (e.g. Twitter) and search (which are about "data" or "communication", and so are not SaaS), and e.g. Google Docs (which does do computation for you, and so is SaaS). (See Stallman's article Who does that server really serve?)
  

• Misuse of an individual's data: essentially doing something with your data without your permission, or even your knowledge - for example, passing on personal data to the authorities, unilaterally modifying your data, or even (for example in the case of Facebook) using it for commercial purposes.

• "The War on Sharing": according to Stallman, sharing is "using the internet for what it's best at", and the war on sharing - whether digital rights management (DRM) technology or threatening internet users with disconnection (as under the UK's Digital Economy Act) - is an attempt by commercial interests to unfairly restrict what users are allowed to do (see Stallman's article Ending the War on Sharing).

• Users don't have a postive right to do things on the internet: essentially, all the activities that users perform on the internet - communications, payment etc - are dependent on organisations who have no obligation to continue providing those services to you.

This is a pretty long list of issues (hopefully I've accurately captured the essence of each), and while many of them can be mitigated by moving to free software; others (for example, monitoring by ISPs) require other solutions - and Stallman admitted that he's quite pessimistic about the future. Aside from that, it was a fascinating and entertaining talk (including the auctioning of a GNU gnu soft toy to raise funds for the Free Software Foundation) and the subsequent audience Q&A session provided many opportunities for elaboration and clarification on many of the issues.

I'm still mulling over many of the issues raised. On the one hand there is a fundamental question about what moral rights you believe individuals should have, both generally and with specific regard to the digital world; and on the other there is the question of what you should do if you feel those rights are not being upheld. Stallman's position is clear and uncompromising: for example, not owning a mobile phone and not using a key card to enter his office (to avoid the possibility of being tracked), and using a netbook that allows him to run 100% free software (down to the BIOS level). It's certainly given me plenty to think about, and I'm looking forward to reading his book of collected essays "Free Software, Free Society" - which might be a good place to start if you're also interested in learning more.

Book review: "Python 2.6 Text Processing: Beginner’s Guide" by Jeff McNeil

Jeff McNeil’s “Python 2.6 Text Processing: Beginner’s Guide” is a practical introduction to a wide range of methods for reading, processing and writing textual data from a variety of structured and unstructured data formats. Aimed primarily at novice Python programmers who have some elementary knowledge of the language basics but without prior experience in text processing, the book offers hands-on examples for each of the techniques it discusses – ranging from Python’s built-in libraries for handling strings, regular expressions, and formats such as JSON, XML and HTML, through to more advanced topics such as parsing custom grammars, and efficiently searching large text archives. In addition it contains a great deal of general supporting material on working with Python, including installing packages and third-party libraries, and working with Python 3.

The first three chapters lay the foundations, covering a number of Python basics including a crash course in file and URL I/O, and the essentials of Python’s built-in string handling functions. Useful background topics – such as installing packages with easy_install, and using virtualenv – are also introduced here. (A sample of the first chapter can be freely downloaded from the book’s website at https://www.packtpub.com/python-2-6-text-processing-beginners-guide/book). The next three cover: using the standard library to work with simple structured data formats (delimited “CSV” data, “ini”-style configuration files, and JSON-formatted data); working with Python regular expressions (a stand out chapter for me); and handling structured markup (specifically, XML and HTML). Subsequent chapters on using the Mako templating package (the default system for the Pylons web framework) to generate emails and web pages, and on writing more advanced data formats (PDF, Excel and OpenDocument), are separated by an excellent overview of understanding and working with Unicode, encodings and application internationalization (“i18n”).

The remaining two chapters cover more advanced topics, with some good background theory supplementing the practical examples: using the PyParsing package to create parsers for custom grammars (with a brief nod to the basics of natural language processing using the Natural Language Toolkit, NLTK); and the Nucular package for indexing large quantities of textual data (not necessarily just plain text) to enable highly efficient searching. Finally, an appendix offers a grab-bag of general Python resources, references to some more advanced text processing tools (such as Apache’s Lucene/Solr), and an excellent overview of the differences between Python 2 and 3 (including a hands-on example of migrating code from 2 to 3).

The book covers a lot of ground and moves fairly quickly; however it adopts a largely successful hands-on approach, engaging the reader with working examples at each stage to illustrate the key points, and this certainly helped me keep up. I was also impressed by the clear and concise quality of code in the examples, and the very natural way that general Python concepts and principles – generators, duck typing, packaging and so on – were introduced as asides. (One very minor criticism is that the layout of the example code could have been improved, as the indentation levels weren’t always immediately obvious to me.) Aside from a surprisingly unsatisfying chapter on structured markup (reluctantly, I would recommend looking elsewhere for an introduction to XML processing with Python) and a few niggling typos, there’s a lot of excellent material in this book, and the author has a knack for presenting some tricky concepts in a deceptively easy-to-understand manner. I think that the chapter on regular expressions is possibly one of the best introductions to the subject that I’ve ever seen; other chapters on encodings and internationalization, advanced parsing, and indexing and searching were also highlights for me (as was the section on Python 3 in the appendix).

Overall I really enjoyed working through the book and felt I learned a lot. I think it’s fair to say that given the rather ambitious range of techniques presented, in many cases (particularly for the more advanced or specialised topics) that the chapters are inevitably more introductory than definitive in nature: the reader is given enough information to grasp the background concepts and get started, with pointers to external resources to learn more. In conclusion, I think this is a great introduction to a wide range of text processing techniques in Python, both for novice Pythonistas (who will undoubtedly also benefit from the more general Python tips and tricks presented in the book) and more experienced programmers who are looking for a place to start learning about text processing.

Disclosure: a free e-copy of this book was received from the publisher for review purposes; this review has also been submitted to Amazon.

Day Camp 4 Developers: Telecommuting

About two weeks ago I took part in the second online Day Camp 4 Developers, on the topic of telecommuting. The idea behind the Day Camp events is to provide software developers with practical knowledge and advice in the area of "soft" skills, to complement their expertise with "hard" skills (i.e. actual coding). In this case five speakers gave consistently excellent web presentations (slides and audio) with different perspectives on remote working, while an IRC chatroom gave all participants a forum to discuss the issues behind the scenes.

Lorna Jane Mitchell started off by asking "Could You Telecommute?". As a teleworker herself, Lorna Jane looked at the environmental, organisational and personal factors that influence the happiness and productivity of the remote worker: for example, ensuring you have a good home working space, and set clear boundaries between work and personal life (both for yourself and for others). In particular you have to be aware of the tendency for other people to think that working from home is easy, and that your time is infinitely flexible. She also noted that there are some big differences between being part of a distributed team and being a telecommuting member of a co-located team (where you risk feeling isolated), and further differences between employees and freelancers. Particularly for lone telecommuters, it's important to build professional and social support networks that might otherwise be taken for granted in more conventional work settings.

Next self-described "entreprenerd" Ivo Jansch talked about "The Business Case For Telecommuting". Ivo's company Egeniq is built around a distributed team (essentially using remote working as an organisational model) - so in addition to benefiting individual workers, he suggested ways that telecommuting could positively impact the company's bottom line, for example enabling access to an bigger talent pool and increasing its geographical reach (if providing consultancy services). He acknowledged that this distributed model won't suit every company or industry however, and success requires (amongst other things) a results-driven culture where individuals are trusted to self-manage and have a sense of shared responsibility. Ultimately good communication between team members is paramount.

After the lunch break, Jack G. Ford gave a manager's perspective on setting up a telecommuting programme in his presentation "Can I Work From Home Tomorrow?". Jack introduced himself as an ex-coder who is now the manager for 17 developers in a more conventional environment than Ivo's, but in spite of that his key points seemed remarkably similar: beyond asking whether the company infrastructure can support remote working, the main issues are trust (both with the manager and with the team) and good communication between the manager and the individual. Jack emphasised that as a manager, when you telecommute, "I can't see you," so the telecommuter must stay connected, keep the manager informed, and must not only act professionally but be seen to do so. Although it might seem obvious, this was a fascinating insight into telecommuting from the other side of the management chain.

Ligaya Turmelle's presentation on "Managing the Work/Life Balance" emphasised the challenges of balancing work and home life, with her lists of "the good, the bad and the ugly" of remote working from a teleworker perspective. Ligaya focused especially on balancing family commitments with work commitments, and among some interesting observations (for example, no longer doing the daily commute means you lose some "me time" to yourself), I was most struck by the admission that if you love your work then it can mean sometimes that you want to go on working, and are in danger of not respecting your own ground rules. While noting that situations can differ both for individuals and companies, her advice was: clarify everyone's expectations (e.g. policies for "on-call" hours, weekends, and holidays); set up ground rules and limits (and be disciplined in adhering to them); and try to be flexible and imaginative in how you approach your work.

The final presentation was Avdi Grimm talking about "The Well-Equipped Remote Worker". Avdi is a freelance software developer who is also a "dispersed teams facilitator" and runs the Wide Teams blog. As might be expected from the title, some of the focus was on the hardware and software tools that can help with remote working, but there was just as much information on practices that can support distributed teams. Once again promoting communication is key, and using tools and practices that help team members create good working relationships (for example, utilising social media like Twitter and Facebook, and holding regular face-to-face meetings) can really contribute to this.

Looking back over all the talks, a few common themes had emerged for me:

• Good communication (both with managers and with other team members) to build trust, keep people informed and avoid misunderstandings;
• Clarify expectations on all sides, and establishing well-defined boundaries between work and personal life. Set ground rules to ensure that those boundaries are respected by others (your boss, your family and friends) and have the discipline to also respect them yourself;
• Build and maintain your social and professional support networks for when there are problem times;
• Provide yourself with a good working environment and (software and hardware) tools.
  

I was also able to relate some points to my own experiences: when I worked briefly as a remote member of a co-located team, I did feel a real sense of isolation; another time as a home teleworker I got the impression from some people that they assumed (not maliciously) that I only did a few hours work a day; and previous experience as part of a large organisation makes me feel that there was some truth in Ivo's comment that "co-location is over-rated", in that it doesn't automatically lead to great communication between individuals or groups.

Overall it was an excellent event and a good use of 8 hours of my Saturday - although the time difference (coincidentally another telecommuting issue) meant that it didn't finish until 10pm UK time I surprised myself by staying with it to the end. Hats off to Cal and Kathy Evans for organising the day and to the speakers for their excellent presentations. Here's waiting for the next Day Camp 4 Developers!

MadLab: pancake café and the Omniversity of Manchester

Yesterday I dropped into the Manchester Digital Laboratory (aka MadLab) in Edge Street for the MadLab Café Pancake Day, and enjoyed a couple of hours chatting to various friendly people while eating an extremely tasty pancake and drinking cups of tea (one of my favourite pastimes), and at one point even discussing Outkast's back catalogue.

MadLab describes itself as "a community space for people who want to do and make interesting stuff - a place for geeks, artists, designers, illustrators, hackers, tinkerers, innovators and idle dreamers; an autonomous R&D laboratory and a release valve for Manchester's creative communities." I'm not sure precisely where I'd put myself in that list - I've only been there a couple of times before, for the Python Northwest user group meetings - but the folks I met seemed to be a representative cross section of the target community.

There's a packed and eclectic schedule of (mostly free) events hosted there, which is well-worth checking out (see http://madlab.org.uk/events/), but their most recent new development is the Omniversity of Manchester - a programme of professional-level training courses that so far have covered experimental film making and physical computing with Arduino, with plans to extend to topics as diverse as web design, Ruby on Rails, writing workshops and urban gardening. These courses won't be free, but the fees will go towards keeping MadLab sustainable and supporting the other free events.

If you're interested in learning more then you can watch out a video, and register the subjects you'd like to see covered by taking a moment to fill in their survey:

• The Omniversity Crowd Sourced Cirriculum Survey

Personally I think it's a really exciting idea - I'm generally a fan of courses, and many of the proposed workshops are things that I'd love to learn more about, so it would also be great to see the Omniversity take off and help MadLab expand and flourish as a focal point for Manchester's digital community - the more people who find out about it and get involved the better. And in the meantime I'll be looking forward to the next (undoubtedly tasty) MadLab café event.

Book review: "Simply SQL" by Rudy Limeback

Rudy Limeback's "Simply SQL" (Sitepoint) is an overview of SQL targeted at web application developers, and intended to fill a gap between the basic "SQL 101"-type tutorials (seemingly compulsory in just about every introductory article or book about web programming) and more advanced texts covering topics which at first glance don't seem so relevant to the straightforward day-to-day requirements of many web applications.

The chapters are grouped into two main sections. The first deals with the details of the SQL language and comprises the bulk of the book. It starts with a short introduction to the SQL commands most commonly needed by web developers to create and modify data within the database (all the usual suspects - CREATE, ALTER, INSERT, UPDATE, DELETE and so on - are quickly dealt with here). The rest of this section focuses on the SELECT command (the one used to retrieve information), with each chapter covering one specific clause - FROM, WHERE, GROUP BY and so on - in quite extensive detail, and illustrated with examples from sample applications.

The second section of the book has three chapters covering some basic database design concepts, specifically SQL data types, relational integrity, and the use of "special structures" (such as tables that refer to themselves) for particular situations. The appendices then outline the basics of using some specific SQL implementations, along with details of the sample applications and scripts used in the main part of the book.

The heavy emphasis on the SELECT statement might seem odd, but it makes a lot of sense in the context of web applications where data is typically read from the database far more than it's written. The detailed examples are also excellent - at times invaluable - for clarifying things like (for example) the nuances of the different types of JOINS, the subtleties of the GROUP BY and HAVING clauses (useful for aggregating data from subsets of rows in conjunction with summing and averaging functions), and the issues with working with time data. I certainly learnt a few things - the GROUP BY clause was completely new to me, as were the distinctions between the FLOAT and DECIMAL data types (DECIMALs are exact - within certain limits - while FLOATs are approximate). I found the brief sections on views, derived tables and subqueries extremely enlightening, as was the discussion of foreign keys in the chapter on relational integrity, and the clear writing style throughout made the book a pleasure to read.

It's important to note that "Simply SQL" is based on the SQL standard, rather than the syntax of specific implementations (although in places it does indicate where there are notable deviations from the standard, particularly for MySQL) - also it doesn't cover any of the programming APIs, so it's not really a reference text (admittedly it doesn't claim to be). However with its clear and detailed explanations it looks like it would be a useful companion to more traditional reference or cookbooks and will definitely reward re-reading - least ways, I'm sure I'll be squeezing plenty more juice out of it in the future. So overall highly recommended.