Dr Administrator

Author's posts

Sep 20 2016

Book review: Beautiful JavaScript edited by Anton Kovalyov

beautiful_javascriptI have approached JavaScript in a crabwise fashion. A few years ago I managed to put together some visualisations by striking randomly at the keyboard. I then read Douglas Crockford’s JavaScript: The Good Parts, and bought JavaScript Bible by Danny Goodman, Michael Morrison, Paul Novitski, Tia Gustaff Rayl which I used as a monitor stand for a couple of years.

Working at ScraperWiki (now The Sensible Code Company), I wrote some more rational code whilst pair-programming with a colleague. More recently I have been building demonstration and analytical web applications using JavaScript which access databases and display layered maps, some of the effects I achieve are even intentional! The importance of JavaScript for me is that nowadays when I come to make a GUI for my analysis (usually in Python) then the natural thing to do is build a web interface using JavaScript/CSS/HTML because the “native” GUI toolkits for Python are looking dated and unloved. As my colleague pointed out, nowadays every decent web browser comes with a pretty complete IDE for JavaScript which allows you to run and inspect your code, profile network activity, add breakpoints and emulate a range of devices both in display and network bandwidth capabilities. Furthermore there are a large number of libraries to help with almost any task. I’ve used d3 for visualisations, jQuery for just about everything, OpenLayers for maps, and three.js for high performance 3D rendering.

This brings me to Beautiful JavaScript: Leading Programmers Explain How They Think edited by Anton Kovalyov. The book is an edited volume featuring chapters from 15 experienced JavaScript programmers. The style varies dramatically, as you might expect, but chapters are well-edited and readable. Overall the book is only 150 pages. My experience is that learning a programming language is much more than the brute detail of the language syntax, reading this book is my way of finding out what I should do, rather than what it is possible to do.

It’s striking that several of the authors write about introducing class inheritance into JavaScript. To me this highlights the flexibility of programming languages, and possibly the inflexibility of programmers. Despite many years of abstract learning about object-oriented programming I persistently fail to do it, even if the features are available in the language I am using. I blame some of this on a long association with FORTRAN and then Matlab which only introduced object-oriented features later in their lives. “Proper” developers, it seems, are taught to use class inheritance and when the language they select does not offer it natively they improvise to re-introduce it. Since Beautiful JavaScript was published JavaScript now has a class keyword but this simply provides a prettier way of accessing the prototype inheritance mechanism of JavaScript.

Other chapters in Beautiful JavaScript are about coding style. For teams, consistent and unflashy style are more important than using a language to its limits. Some chapters demonstrate just what those limits can be, for example, Graeme Roberts chapter “JavaScript is Cutieful” introduces us to some very obscure code. Other chapters offer practical implementations of a maths parser, a domain specific language parser and some notes on proper error handling.

JavaScript is an odd sort of a language, at first it seemed almost like a toy language designed to do minor tasks on web pages. Twenty years after its birth it is everywhere and multiple billion dollar businesses are built on top of it. If you like you can now code in JavaScript on your server, as well as in the client web browser using node.js. You can write in CoffeeScript which compiles to JavaScript (I’ve never seen the point of this). Chapters by Jonathan Barronville on node.js and Rebecca Murphey on Backbone highlight this growing maturity.

Anton Kovalyov writes on how JavaScript can be used as a functional language. Its illuminating to see this discussion alongside those looking at class inheritance-like behaviour. It highlights the risks of treating JavaScript as a language with class inheritance or being a “true” functional language. The risk being that although JavaScript might look like these things ultimately it isn’t and this may cause problems. For example, functional languages rely on data structures being immutable, they aren’t in JavaScript so although you might decide in your functional programming mode that you will not modify the input arguments to a function JavaScript will not stop from you from doing so.

The authors are listed with brief biographies in the dead zone beyond the index which is a pity because the biographies could very usefully been presented at the beginning of each chapter. They are: Anton Kovalyov , Jonathan Barronville, Sara Chipps, Angus Croll, Marijn Haverbeke, Ariya Hidayat, Daryl Koopersmith, Rebecca Murphey, Danial Pupius, Graeme Roberts, Jenn Schiffer, Jacob Thorton, Ben Vinegar, Rick Waldron, Nicholas Zakas. They have backgrounds with Twitter, Medium, Yahoo and diverse other places.

Beautiful JavaScript is a short, readable book which gives the relatively new JavaScript programmer something to think about.

Sep 09 2016

Book review: The Runner’s Handbook by Bob Glover

runnershandbookI took up running a year or so ago, on May 2nd 2015 – to be precise. I know this because the first thing I did when I started running was buy a fancy GPS runner’s watch. I started because I wasn’t very fit, and the gym was expensive and didn’t really fit around my available time. You can see some statistics on my running in my earlier blog post. Not long after getting the watch I bought some proper running shoes and since then I’ve lost 10kg and gone from “running” 5km in something over 30 minutes to running 10km in under 50 minutes.

But I’ve got a bit jaded and stuck in my running ways, so I thought I’d get The Runner’s Handbook by Bob Glover to help me with my next steps. There are a wide range of guides on the internet, but I’m a committed book buyer. Running is pretty much my only exercise, although I cycle 40 miles to work and back most weeks this is at a fairly leisurely pace. I’m aware that the lower half of my body, heart and lungs are quite fit but the rest is not – sort of like and inverted Popeye.

There is an early opportunity to test your current fitness with some standard exercises in The Runner’s Handbook. It turns out I’m in the top 25% for running speed over 1.5 miles which makes me an intermediate runner, but linger in the lower half for upper body strength and flexibility. To be honest, the push-ups test left me aching for several days after my over-enthusiastic efforts!

The Handbook is pretty comprehensive, 700 pages of comprehensive. It covers fitness, and the motivation for getting fitting, running programmes for different standards of runner, training for races, all the way up to the marathon distance and also training for speed. I read the first 250 or so pages covering these topics and a further 100 or so on Running form and Supplemental Training. I’ve skipped sections on food and drink, running environment, running lifestyle, special runners and illness and injury. I can always dip into them if the need arises.

The writing is very readable, Glover chatters his way through the book half in conversation with his co-author Jack Shepherd. Glover is a real enthusiast for his sport. He has trained many amateur runners, and you get a feel for New York state and the New York Marathon through his writing. He introduces some of the history of the modern running movement, dedicating the book to Fred Lebow who took the New York Road Runners Club from 200 members to over 30,000. He also took the New York Marathon out of Central Park and into the city, a pattern subsequent repeated around the world.

Glover also dedicates the book to Nina Kuscsik, who was instrumental in getting women admitted to longer distance races, starting with her own run in the 1972 Boston marathon, which was accompanied by significant male protest. I was bemused to read that the original sports bra was constructed in the late 1970s by stitching two jockstraps together.

As a result of reading the boo I have a set of stretches and upper body strengthening exercises to try out. The sections covering these are a bit repetitive and could really have done with some diagrams. Fortunately, having introduced dozens or exercises Glover does provide a sample work out with a more manageable set of things to do. I must admit one of my problems with running is that I try to go faster with every run I do. Reading The Handbook has backed me off from this futile quest. Now I can go out for a run and not feel I’ve failed if I don’t beat my previous fastest time.

The second thing I’ve learned is that I have to get a heart rate monitor! Okay, so Glover says I could do some crude manual measurement involving feeling my pulse and counting but where’s the fun in that? The idea being that you are in cardiovascular training mode when you reach something like 70-80% of your maximum heart rate. I have my eye on the Garmin Forerunner 235 or maybe the cheaper Garmin Forerunner 35. These both have light-based heart monitors under the wristband of the watch rather than the more usual (and cumbersome) chest monitors. By the way, you’re not going to read about the very latest gadgets in Glover’s book – this edition is from 1996 but it doesn’t feel at all dated.

This was the right sort of book for me, it is comprehensive and authoritative, it reads well and there are some things I can go away and do now to improve my running.

Aug 29 2016

Book review: Essential SQLAlchemy by Jason Myers and Rick Copeland

sqlalchemyEssential SQLAlchemy by Jason Myers and Rick Copeland is a short book about the Python library SQLAlchemy which provides a programming interface to databases using the SQL query language. As with any software library there is ample online material on SQLAlchemy but I’m old-fashioned and like to buy a book.

SQL was one of those (many) things I was never taught as a scientific programmer, so I went off and read a book and blogged about it (rather more extensively than usual). It’s been a useful skill as I’ve moved away from the physical sciences to more data-oriented software development. As it stands I have a good theoretical knowledge of SQL and databases, and can write fairly sophisticated single table queries but my methodology for multi-table operations is stochastic.

I’m looking at using SQLAlchemy because it’s something I feel I should use, and people with far more experience than me recommend using it, or a similar system. Django, the web application framework, has its own ORM.

Essential SQLAlchemy is divided into three sections, on SQLAlchemy Core, SQL Alchemy ORM and Alembic. The first two represent the two main ways SQLAlchemy interacts with databases. The Core model is very much a way of writing SQL queries but with Pythonic syntax. I can see this having pros and cons. On the plus side I’ve seen SQLAlchemy used to write, succinctly, rather complex join queries. In addition, SQLAlchemy Core allows you to build queries conditionally which is possible by using string manipulation on standard queries but requires some careful thought which SQLAlchemy has done for you. SQLAlchemy allows you to abstract away the underlying database so that, in principle, you can switch from SQLite to PostgresQL seamlessly. In practice this is likely to be a bit fraught since different databases support different functionality. This becomes a problem when it becomes a problem. SQLAlchemy gives your Python programme a context for its queries which I can see being invaluable in checking queries for correctness and documenting the database the programme accesses. On the con side: I usually know what SQL query I want to write, so I don’t see great benefit in adding a layer of Python to write that query.

SQLAlchemy Object Relational Mapper (ORM)  is a different way of doing things. Rather than explicitly writing SQL-like statements we are invited to create classes which map to the database via SQLAlchemy. This leaves us to think about what we want our classes to do rather than worry too much about the database. This sounds fine in principle but I suspect the experienced SQL-user will know exactly what database schema they want to create.

Both the Core and ORM models allow the use of “reflection” to build the Pythonic structures from a pre-existing datatabase.

The third part of the book is on Alembic, a migrations manager for SQLAlchemy, which is installed separately. This automates the process of upgrading your database to a new schema (or downgrading it). You’d want to do this to preserve customer data in a transactional database storing orders or something like that. Here I learnt that SQLite does not have full ALTER TABLE functionality.

A useful pattern in both this book and in Test-driven Development is to wrap database calls in their own helper functions. This helps in testing but it also means that if you need to switch database backend or the library you are using for access then the impact is relatively low. I’ve gone some way to doing this in my own coding.

The sections on Core and ORM are almost word for word repeats with only small variations to account for the different syntax between the two methods. Although it may have a didactic value this is frustrating in a book already so short.

Reading this book has made me realise that the use I put SQL to is a little unusual. I typically use a database to provide convenient access to a dataset I’m interested in, so I do a one off upload of the data, apply indexes and then query. Once loaded the data doesn’t change. The datasets tend to be single tables with limited numbers of lookups which I typically store outside of the database. Updates or transactions are rare, and if I want a new schema then I typically restart from scratch. SQLite is very good for this application. SQLAlchemy, I think, comes into its own in more transactional, multi-table databases where Alembic is used to manage migrations.

Ultimately, I suspect SQLAlchemy does not make for a whole book by itself, hence the briefness of this one despite much repeated material. Perhaps, “SQL for Python Programmers” would work better, covering SQL in general and SQLAlchemy as a special case.

Aug 20 2016

Book review: Test-Driven Development with Python by Harry J.W. Percival

test-drivenTest-Driven Development with Python by Harry J.W. Percival is a tutorial rather than a text book and it taught me as much about Django as testing. I should point out that I wilfully fail to do the “follow along with me” thing in tutorial style books.

Test-driven development (TDD) is a methodology that mandates writing tests first before actual code that does stuff. The first tests are for the desired behaviour that will be presented to the user.

I was introduced to software testing very early in my tenure ScraperWiki, now The Sensible Code Company. I was aware of its existence prior to this but didn’t really get the required impetuous to get me started, it didn’t help that I was mostly coding in Matlab which didn’t have a great deal of support for testing at the time. The required impetus at ScraperWiki was pair programming.

Python is different to Matlab, it has an entirely acceptable testing framework built-in. Test-driven Development made me look at this functionality again. So far I’ve been using the nose testing library but there is a note on its home page now saying it will not be developed further. It turns out Python’s unittest has been developing in Python 3 which reduces the need for 3rd party libraries to help in the testing process. Python now includes the Mock library which provides functions to act as “test doubles” prior to the implementation of the real thing. As an aside I learnt there is a whole set of such tests doubles including mocks, but also stubs, fakes and spies.

Test-driven Development is structured as a tutorial to build a simple list management web application which stores the lists of multiple users, and allows them to add new items to the lists. The workflow follows the TDD scheme: to write failing tests first which development then allows to pass. The first tests are functional tests  of the whole application made using the Selenium webdriver, which automates a web browser, and allows testing of dynamic, JavaScript pages as well as simple static pages. Beneath these functional tests lie unit tests which test isolated pieces of logic and integrated tests which test logic against data sources and other external systems. Integration tests  test against 3rd party services.

The solution is worked through using the Django web framework for Python. I’ve not used it before – I use the rather simpler Flask library. I can see that Django contains more functionality but it is at the cost of more complexity. In places it wasn’t clear whether the book was talking about general testing functionality or some feature of the Django testing functionality. Django includes a range of fancy features alien to the seasoned Flask user. These include its own ORM, user administration systems, and classes to represent web forms.

Test-driven Development has good coverage in terms of the end goal of producing a web application. So not only do we learn about testing elements of the Python web application but also something of testing in JavaScript. (This seems to involve a preferred testing framework for every library). It goes on to talk about some elements of devops, configuring servers using the Fabric library, and also continuous integration testing using Jenkins. These are all described in sufficient detail that I feel I could setup the minimal system to try them out.

Devops still seems to be something of a dark art with a provision of libraries and systems (Chef, Puppet, Ansible, Juju, Salt, etc etc) with no clear, stable frontrunner.

An appendix introduces “behaviour-driven development” which sees sees a test framework which allows the tests to be presented in terms of a domain specific language with (manual) links to the functional tests beneath.

In terms of what I will do differently having read this book. I’m keen to try out some JavaScript testing since my normal development activities involve data analysis and processing using Python but increasingly blingy web interfaces for visualisation and presentation. At the moment these frontends are slightly scary systems which I fear to adjust since they are without tests.

With the proviso above, that I don’t actually follow along, I like the tutorial style. Documentation has its place but ultimately it is good to be guided in what you should do rather than all the things you could possibly do. Test-driven Development introduces the tools and vocabulary you need to work in a test-driven style with the thread of the list management web application tying everything together. Whether it instils in me the strict discipline of always writing tests first remains to be seen.

Aug 17 2016

Book review: The Book of the Edwardian & Interwar House by Richard Russell Lawrence

edwardiandI’m currently working on providing some data for domestic properties, mainly for the purpose of making the process of getting a buildings insurance quote easier. One of the parameters the insurance industry is interested in is the age of a home.

And so I came to The Book of the Edwardian & Interwar House by Richard Russell Lawrence. I picked the book up partly out of curiosity but I also hoped to pick up some ideas as to how I might date a house based on the information to hand.

The book starts with some general comments about the period and what had gone before, leading to a discussion of Edwardian architecture. This is followed by a similar discussion of interwar architecture. The book finishes with a whole load of short chapters on individual elements of the home, bricks, tiles, lighting, wireless and telephone and so forth. As well as simple domestic architecture there is some discussion of high end homes of the period.

The second half of the 19th century saw the expansion of British cities, driven by industrialisation and enabled by the growing railway system and, for the capital, the London Underground. This led to the building of an awful lot of terraced houses at high densities, generally to be rented to workers. The 1877 Model Bye-laws Act and the 1878 Building Act set some requirements on how houses could be built in terms of their size, distance from facing houses and sanitary facilities.

This situation continued into the beginning of the 20th century, with a growing middle class looking for better homes than the terraces offered. The First World War brought house building to a complete stop, after the war there was a housing shortage of something like 850000 properties and a fear in government that there would be fighting on the streets if “Homes Fit for Heroes” were not supplied. The Interwar period saw a huge increase in home ownership, the building of 4 million homes (the majority semi-detached) and the first council houses. Public housing was built following the specifications of the Tudor Walters Report (1918), which specified a minimum size of 760 square feet, a maximum density of 12 houses per acre and preferred wider houses, semi-detached or in short terraces. Private housing sought to differentiate in stall from public housing but could scarcely offer poorer specifications.

This is interesting because sizes and spacings of buildings can be determined from the Ordnance Survey’s mapping data.

Earlier regulations, following the Great Fire of London, had banned the building of timber-framed houses in cities and windows had to be recessed in their openings for similar reasons. This, and details such as how bricks are laid, can give further information on building age but they are not readily amenable to automation or determinable from public data.

Gross style seems to be of relatively little help when dating buildings, many Edwardian and Interwar houses were built in neo-Georgian style which as the name implies can look very Georgian. Also popular was Tudorbethan which emulated an old English style with mock, black wooden beams painted or nailed to a white exterior. Chester’s city centre is rife with an elaborate form of this style, mainly built in the Edwardian or very late Victorian period, although there are some examples of the genuine article.

Internally, the period saw the evolution of the kitchen, scullery and kitchenette as new-fangled gas and electric ovens replaced old ranges. There was also a discussion as to whether buildings for workers should have a separate parlour and living room. I’m well aware that my grandparents generation would often reserve a room for “best”, which as family did not get invited into.

It struck me as I read The Book that houses I would have been fairly confident were post-Second World War I now suspect are interwar. It surprised me that modest houses started to get a garage as an option as early as the 1930s, the big increase in car ownership had started before the First World War, a bit earlier than I expected.

I learnt some new useful vocabulary, a “catslide” roof is one on a two storey house which terminates at the top of the first storey. A “hipped” is one that has slopes on more that two sides, rather than having gable ends (previously I’d have called this a “roof”).

This is something of a coffee-table book, with lots of photographs, I found the text in the early part more readable than the long litany of descriptions of individual architectural details. I have a few ideas to try out on the dating of houses.