Hannah Clare Wray Hazi

I love making beautiful things.

Jun 16, 2022

CodeLand 2022

Code Newbie I spoke at a virtual conference!

I was recently invited to speak at Code Newbie's CodeLand 2022. I had a wonderful time at the virtual conference and got the chance to speak with some great people including experts in the field (I was part of a roundtable discussion with Kelsey Hightower, I was starstruck!). Code Newbie's community is a lovely welcoming place for everyone, especially folks who are just getting started in software professionally. I'm definitely interested to go along again next year.

If you'd like to watch my talk, it's still available on demand here

Mar 13, 2021

May 22, 2020

Unexploded Bombs

Masts Masts of the SS Richard Montgomery. Photo by Clem Rutter, Rochester, Kent CC BY

I'd like to introduce you to the SS Richard Montgomery. For those who don't know the story already, it's quite extraordinary.

Towards the end of WWII, a Liberty Ship, the SS Richard Montgomery, ran aground on shifting sands just off the coast of Sheerness at the mouth of the Thames Estuary. She was loaded with over 6,000 tonnes of high-explosive bombs and detonators. Salvage operations managed to remove some of the explosives, but before the ship could be made safe it sank further and salvage was abandoned. The ship and her thousands of tonnes of remaining explosives was then left to sit for over 75 years. She is still there.

One of the most remarkable things about the wreck is her location. She lies in shallow water just 2.4 km from the seaside town of Sheerness. Not only that, but she is less than 200m from a busy shipping lane, and remarkably close to the Grain Liquid Natural Gas Terminal, the largest Liquified Natural Gas facility in Europe.

How dangerous is it?

WWII ordinance turns up every now and then during construction projects. Some unexploded WWII grenades were discovered while building an ice rink in my home town of Cambridge. The discovery triggered a visit from the bomb disposal squad and emergency services, alongside a limitation on flights in and out of Cambridge Airport until the grenades could be made safe.

But the amount of unexploded munitions here is in an entirely different category. There are no clear records of how much ordinance was left on the ship, but according to an official MCA report the ship likely contains more than 9000 explosives including cluster bombs and hundreds of giant 2,000lb 'blockbuster' bombs.It's hard to comprehend their explosive power should they go off.

A New Scientist investigation from 2004 suggests that spontaneous detonation of the entire cargo would hurl a column of debris up to 3 kilometres into the air, send a tsunami barrelling up the Thames and cause a shock wave that would damage buildings for miles around, including the liquid gas containers on the nearby Isle of Grain, which could detonate in turn.

What happens next?

Map of location Suggested locations of new airport in Thames Estuary. By Ordnance Survey with modifications by Prioryman CC BY 3.0

Some demolition experts are content to let the wreck lie, hoping that time and tide will reduce the deadliness of her cargo. They argue that any attempt to clear the bombs from the wreck would be riskier than letting her lie. These arguments give the example of the explosion of the Kielce, a smaller munitions wreck which was more than 6km out to sea. A failed salvage operation there in 1967 set off an explosion that measured 4.5 on the Richter scale and damaged property in nearby Folkestone.

However, others disagree and argue that the wreck is actually becoming more dangerous over time. Phosphorous is now apparently leaking from the munitions aboard, evident as flames on the surface of the water where it burns in contact with air. These can sometimes be seen at night by local residents.

Another possibility is a collision. There have already been at least 22 near-misses where shipping traffic only just steered away from the exclusion zone around the wreck in time. One particularly harrowing episode occurred in May 1980 when a Danish chemical tanker, 'Mare Altum', steered aside only minutes before she would have impacted the Montgomery.

There have been persistent questions in Parliament asked about the subject. Recent surveys suggest that the condition of the wreck is rapidly deteriorating, which might lead to a sudden catastrophic collapse. Dave Welch, a former Royal Navy bomb disposal expert, who has advised the government on the SS Richard Montgomery's munitions, says:

"We can’t continue just leaving the wreck to fall apart. Somebody at some point in the next five to ten years is going to have a very difficult decision to make and I would say the sooner it’s made, the easier and cheaper it will be as a solution."

So far, no solution is in sight.

How does this relate to programming, anyway?

Every codebase has its unexploded bombs. Not so potentially serious as the SS Richard Montgomery, perhaps. But our code is out there driving all sorts of things in the real world. If we neglect potentially serious problems, we can harm people just as easily as other kinds of engineers.

Take your bug reports seriously

It can be too easy to dismiss user reports of bugs or accidental misuses of your application. Because we are so familiar with our own code, it can lead to a feeling of contempt for the person who doesn't approach the software in the same way that we do, or have as much knowledge about the underlying structure. And there is of course a natural feeling of defensiveness toward our own work. It can be humbling to find a bug in what you had hoped was well-crafted code, a blow to your ego and confidence as a programmer, perhaps.

This kind of misplaced confidence can be lethal. In the Therac-25 Incidents at least 6 cancer patients were given hundreds of times the desired dose of radiation therapy. This resulted in serious injuries and deaths. The malfunctions were reported early to the manufacturer, who sent engineers to a hospital where one of the lethal accidents occurred. They spent a day running the machine through tests but could not reproduce the critical malfuction, code 54, which only appeared when users typed with a certain fast frequency as experienced operators sometimes could. Because the error that caused the lethal bug was not observed by company investigators, they concluded it was "not possible for the Therac-25 to overdose a patient". It took another tragic accidental death to prove them wrong. This excellent analysis of the accidents dissects the timeline of events and has valuable lessons for us, particularly medical software developers.

We can be falsely confident about our code fixes, too, thinking that they resolve an issue when really they don't. It takes a particular critical, persistent mindset to debug a system well and really fix what the root of a problem was. The excellent rules of thumb in Dave Agans' 'Debugging' book are something I return to time and again when tackling software problems. I encourage you to print out the poster and put it on your wall! One of his key points is that until you can reliably trigger a bug, you don't know what the true cause is or whether a fix has addressed the bug or not. Intermittent faults which only appear under certain conditions, like the problems with Therac-25, can be the hardest things to address.

Listen to the voice of inexperience

Listen to newcomers - interns, new starters, people approaching a piece of the code they haven't worked on before. It's very easy to become habituated to a worrying situation - to live atop an unexploded bomb - and sometimes the only way to snap out of your ingrained habit of dismissing a problem is to listen to someone new worry about it.

I would argue that part of the onboarding process for programmers joining a new team should be to ask them what 'unexploded bombs' they might see in the code. There's usually a "and do you have any questions for us" stage in an internship check-in, for instance, but we rarely take the feedback we recieve this way seriously, or get enough detail to understand what about the codebase might be confusing or painful to work with.

Doing a 'Code Walk' structured walkthrough of the code can be very illuminating. (I highly recommend this talk by Mary Chester-Kadwell - it has really shaped the way I teach and learn about new codebases). In the process, pay attention to the questions your new team-mate asks and reflect on what they say about the health of the different parts of your codebase. Is there anything where when you explain it aloud, it seems convoluted and awkward, or counter-intuitive? Anywhere you particularly wish there was documentation to show your new recruit? Those places may be where problems are lurking.

Pay attention to the jokes

Mermaid of Sheerness Mural by Dean Tweedy made for the Promenade Arts Festival in 2015 - photo Andy Hebden

Matt Brown, chairman of Sheerness Enhancement Association for Leisure, condemned the mural in the local newspaper, saying:

"If I was a family visiting, whether I knew about the Montgomery or not, I wouldn’t want to be sitting at the leisure park with the kids being reminded you have those explosives out there."

The artist rebutted: "I wanted to make people aware of the Montgomery as it’s part of Sheerness. Some people would like to deny its existence."

The mermaid makes some local people uncomfortable because it reveals a truth about their town they'd rather not have to acknowledge - the ever-present danger to their lives from the offshore explosives. For a certain kind of authority figure, the reminder of a dangerous situation is worse than the actual danger, because without the reminder they can continue to live their lives without having to address the elephant in the room.

XCKD Data Pipeline This xkcd strip about data pipelines makes me laugh - but it also makes me think about the robustness of my code.

Sometimes the equivalent of a Sheerness Mermaid Mural is the only way you can spot a problem that's become engrained in the way your code is put together. Is there a particular XKCD or Dilbert cartoon that seems to epitomise the bugs and problems you're encountering? Perhaps all the developers working on a particular part of the codebase have a set of in-jokes describing the way a certain class behaves itself? A kind of gallows humour about how a module is annoying to use, something that makes you cringe because it's a little too accurate?

These are all clues to what might be underlying dysfunctions of your code. By paying attention to them, you might be able to spot an unexploded bomb and defuse it, before your users discover it and blow things sky-high.

Sep 16, 2019

Telling Stories With Python And Ren'Py

This is a write-up of a workshop I've given at CamPUG and PyCon UK 2019. It was a lot of fun to deliver, and my participants came away with their own mini-games written in Ren'Py. I was impressed by the range of creative stories, everything from getting lost in Cardiff, storming Area 51, coaxing a grumpy cat, visiting a music festival, going to space, defeating animated fleas, visiting every pub in Cambridge, a child's guide to the Divine Right of Kings, interactive graffiti and more!

I hope this post will be useful as a reference for workshop participants and those who couldn't make it along.

What is Interactive Fiction?

You might be familiar with the concept of interactive fiction from "Choose Your Own Adventure" books.

Ever since computers came on the scene there has been interactive fiction here, too. Zork, one of the earliest examples, is a dungeon-crawling game where the player explores The Great Underground Empire by typing text commands.

Using later tools like Parchment and Twine people are still creating these text-based interactive fiction games. A text-based game I've enjoyed recently is Moonlit Tower by sci-fi author Yoon Ha Lee.

Visual Novels are a genre of interactive fiction that combines pictures and text as a storytelling tool. They originated in Japan and many famous examples such as Fate/Stay Night and Symphonic Rain are Japanese. These games are often romance or relationship-themed, each path perhaps leading to a relationship with a different character.


Ren'Py Icon

Ren'Py is a visual novel creation engine written in Python. It has its own syntax and style, but also allows you to embed pure Python for more complex gameplay mechanics.

It is cross-platform and works on Mac, Linux and Windows. All that you need alongside it is a simple text editor that can convert tabs to spaces, such as gedit.

What can you do in Ren'Py?

Label Jump For Branching Stories

Road Not Taken Screenshot

I would humbly suggest my own game The Road Not Taken as a useful introduction to the label / jump mechanic. Take a look in the script.rpy file to follow how the game works. It demonstrates how menus work in the game and how you can use them to move to different choices, similar to a GOTO statement. It also includes an example of embedding music within gameplay to add a mood to a scene. Feel free to copy and modify it as a basis for your own games.

Custom GUI

Hotel Shower Knob Screenshot

Hotel Shower Knob, a game where you have to puzzle out an unfamiliar hotel bathroom to take a shower, is a good example of a custom GUI. Inside options.rpy the creator replaced the usual cursor with a custom image of a hand:

## The mouse clicker thingy.

define config.mouse = { 'default' : [ ('cursor.png', 66, 95)] }

This makes for a unique visual experience. As the hand is Creative-Commons licenced, you could use it in your own games, too!

Embedded Python

Two Worlds Screenshot

Because Ren'Py is written in Python (2.7, if you're interested) it's easy to embed Python statements within it to acheive more complex effects such as creating mini-games. There are two ways to do this - prefixing single lines with $ or using an indented block with the python: statement. I used python: statements within Ren'Py to create Card objects for my game Two Worlds.

The key thing to notice is the definition of the Card class:

# Define the card objects used to play the games with

        flowers = ["card-front-land-flower%d.png" % i for i in range(1, 3)]

        class Card(object):
            def __init__(self):
                self.face_up = False
                self.selected = False
                self.number = 0
                self.coords = [0, 0]
                self.back = "card-back-land.png"
                self.front = flowers[0]
                self.paired = False

            def coord_text(self):
                return "{}, {}".format(self.coords[0], self.coords[1])

This happens during the init: block, before the game starts, so it is available from the beginning. I subsequently used this in the sea_game.rpy and land_game.rpy files using the ui.interact() statement and action If to connect it with Ren'Py responses to on-screen clicks.

Persistent Data

Another useful trick is the ability to store persistent data between plays of the game.

Example From Long Live The Queen An example from Long Live The Queen

This allows more satisfying gameplay such as unlocking new routes after a complete playthrough, and keeping track of player stats like Strength or Skill. Anything that can be pickled is suitable for this treatment. A simple example:

if persistent.secret_unlocked:
        scene secret_room
        e "I see you've played before!"

To unlock this path the user must hit a piece of code that sets $persistent.secret_unlocked = True

persistent is a special keyword in Ren'Py, so you shouldn't use it for anything else. Unlike other variables, if you haven't yet initialised it when you reach the if statement Ren'Py won't complain.

Useful sources of free images and sounds for your games

There are various community projects to collect images and sound to use in games with Creative Commons or similar licences.

I've found px here a useful collection of images, particularly photos.

I used Fraqtive to create the card images and backgrounds for Two Worlds.

Useful sound sources include Free Music Archive and for sound effects, Free Sound

Example games written in Ren'Py

Benthic Love – Michaela Joffe, Sonya Hallett

Hotel Shower Knob – Yoss III

Death And Burial Of Poor Cock Robin – Lernakow

Long Live The Queen – Hanako Games

And check out the NaNoRenO game jam each year during the month of March – or better still, take part!

Apr 12, 2019

Agile Workshop

I recently attended a Certified Scrum Master course taught by Tobias Mayer of Adventures With Agile. I really enjoyed the course and the style in which it was taught. There was no death by Powerpoint! Tobias actually constructed a board on the wall with columns to keep track of the tasks comprising the course, and we added extra task cards for further discussion and questions as we went along.

The board Here's what the board looked like near the start of the two day course.

We held 'Sprints' of an hour or so at a time, diving into aspects of Agile and then reviewing how it went, to improve our group process. Sometimes the teacher would stand and talk about a concept for a while, but mostly the course was interactive, especially during the second day where we broke out into groups for longer sessions.

The exercises we did included 'Point and Go': a game where players stand in a circle and have to

  • Point to someone else whose place you want to take
  • Wait for them to say "Go"
  • Start moving forwards to them
  • Before you reach them, they have to find another place to go (and the cycle continues!) This was unexpectedly hard! It was a metaphor for how difficult it can be to break out of an established pattern of behaviour at work. Even once we got into a rhythm, if things sped up or someone panicked, our orderly pattern fell apart.

Another exercise I enjoyed was coming up with different metaphors for Scrum. We broke out into groups and thought up some different ideas - I was impressed by the variety and how each of them fitted different parts of what Scrum can look like. Some of my favourites were:

  • a garden growing and changing over time
  • a cocktail bar developing new drinks
  • a stand-up comedian working on their routine
  • a graffiti crew making a work of art for their neighbourhood
  • Jurassic Park (this was mine!)

A Product Owner is like a Duchess A mindmap from my notes about the different Scrum roles

Following the training, I'm a Certified Scrum Master. There have been some intelligent criticisms of this certification process, including by some of its founders. The fact that there is a certification exam seems to somewhat devalue the training experience itself. I didn't really need to complete the training to do the certification exam - its questions are purely based on the Scrum Guide and a few on the Agile Manifesto. How well can a multiple-choice test about a short document really hope to measure someone's competence in such a fuzzy relationship-centred domain as taking on the role of a Scrum Master? It's always going to fall short, I think. I've acted as a Scrum Master for several years already without the certification, so I was interested to see what it covered and didn't touch on.

I passed the exam. But the things that will really stay with me are the advice of the trainer and the discussions I had during the course, especially with others whose companies are also on the path to adopting more Agile practices. I certainly recommend Tobias as a teacher: his creative exercises and the way he presented the course helped grow my understanding and confidence in the role of Scrum Master. I'd like to attend his Scrum Master Clinic - I think it will really help to have that ongoing mentoring and peer advice.

Feb 10, 2019

Flex and Bison

I recently started to learn about flex and Bison - a set of parser creation tools for C, C++ and Java. By specifying the grammar and rules for parsing inside two files, blah.y and blah.l, the flex and bison command-line Linux tools will auto-generate an appropriate parser in your chosen language. As you might imagine, this is very handy.

Since it's generally better to show rather than tell when it comes to software tools, here's a toy project I've been playing with in which I'm using them to parse GCODE.

The flex part is what's called a lexical analyser - it uses regular expressions to split the input into tokens. These tokens are used to generate a parser with the Bison part, which is the grammar that tells the parser what do do when certain tokens are read side by side.

What particularly struck me about these tools was just how old they are.

Elegant weapons ...

Bison is a descendant of a tool called Yacc (Yet Another Compiler Compiler) which was developed by Steven Johnson working for Bell Labs back in the early 1970s, inspired by Donald Knuth's work on LR parsing. It has been rewritten in many different languages over the years, but the most popular implementation these days is probably Bison, which dates back to 1985, when it was worked on by Robert Corbett. Richard Stallman (yes, that Richard Stallman) made the GNU-Bison tool Yacc-compatible.

Flex meanwhile was written in C by Vern Paxson in 1987, tranlating an older tool called Lex. Lex was originally written by Mike Lesk and Eric Schmidt, and described in a paper by them in 1975. It was initially written in ratfor, an extended version of Fortran popular at the time.As they point out in the paper:

"As should be obvious from the above, the outside of Lex is patterned on Yacc and the inside on Aho’s string matching routines. Therefore, both S. C. Johnson and A. V. Aho are really originators of much of Lex, as well as debuggers of it. Many thanks are due to both. The code of the current version of Lex was designed, written, and debugged by Eric Schmidt"

As you might expect of such venerable tools, they have some excellent tutorials on their use, including an O'Reilly book "flex & bison" - which itself is the "long awaited sequel" to the O'Reilly classic, "lex & yacc". Those who teach in depth about these tools or about parsing are in some danger of re-writing them even more nicely in a favourite language - the linked example is PLY, which was originally developed in 2001 for use in an Introduction to Compilers course where students used it to build a compiler for a Pascal-like language.

I'm fascinated by how tools like this have survived and thrived over what, to computer science, is an enormous amount of time. Perhaps it is because they are beautiful - they have some inherent quality that shines out, no matter what language they happen to be in. I was re-reading the interview with Fran Allen in 'Coders At Work' about beautiful code, and it really resonated.

Allen: One of the things I remember really enjoying is reading the original program - and considering it very elegant. That captured me because it was quite a sophisticated program written by someone who had been in the field a while - Roy Nutt. It was beautifully written. Seibel: What makes a program beautiful? Allen: That it is a simple straightforward solution to a problem; that has some intrinsic structure and an obviousness about it that isn't obvious from the problem itself. I picked up probably a new habit from that of learning about programming and learning about a new language by taking an existing program and studying it. Seibel: How do you read code? Let's say you're going to learn a new language and you find a program to read - how do you attack it? Allen: Well, one example was one of my employees had built a parser. This was later on for the PTRAN project. And I wanted to understand his methods. It's actually probably the best parser in the world - now it's out in open source, and it's really an extraordinary parser that can do error correction in flight. I wanted to understand it, so I took it and I read it. And I knew that Phillipe Charles, the man who had written it, was a beautiful programmer. The way I would approach understanding a new language or a new implementation of some very complex problem would be to take a program from somebody that I knew was a great programmer, and read it.

Dec 31, 2017

The Knowledge in the Code

My colleagues and I were discussing legacy code the other day. Someone gave the pretty common opinion that, if there was time, they would of course completely re-write all the legacy code they came across, from scratch. But, since this is not an ideal world and time is limited, they would settle for refactoring what they could. It got me thinking about how my own attitude toward legacy code has changed over time, and why that is.

Indiana Jones and the Lost Code

I spent one summer at university working on a classic legacy code problem. A scientist had written a large piece of Fortran 95 to simulate a manufacturing process for my employers. He had long since retired and there was no way to contact him to ask about his work. As an intern I was asked to add a little bit of extra functionality. They were still using the code and found it reliable, but wanted to add a feature. I felt like an archaeologist, dusting off terse variable names and cryptic comments, trying to understand not only this code but the complex processes it was simulating, too. It was very difficult to get anywhere.

Uncovering the secret of the Lost Code I wonder if I can replace this function without adding test coverage?

My initial reaction - rewrite it! I think most programmers share this instinct. My idea was to tear it down completely and rebuild it, preferrably in a different, more modern language. Then, I felt, I could add the features that were needed. But my manager was adamantly against this. As a summer intern, I would leave soon anyway. If I rewrote the code in another language, where was the benefit to the company? From their perspective, they already had a tool that worked fine. They just needed someone to understand what they already had and improve it a bit. At the time I was frustrated by this. I would tell others the tale with a wistful air - "If only I had had the time to rewrite it properly" I would think, "it would have been so much better". But would it have?

Why Rewrite Code?

I've come across a few different reasons for re-writing code completely. None of them really convince me of their merits anymore.

  • To write it in a new language.

The new language is considered to be 'better' - it has features you want, or the old language is considered passe. Fortran 95 certainly wasn't the best language to be writing new code in anymore! For one thing, there was a severe restriction on variable and routine name lengths - in order to maintain backward compatibility with earlier versions of the language, none of the variables was over 6 characters in length, which didn't aid readability. But most cases aren't as clear-cut as this - I think most people wouldn't choose to re-write a large C program in Rust even if they think Rust is a superior language in some respects.

  • For understanding.

No-one can figure out how the old code works, so we have the idea to learn by doing and completely rewrite it. It's certainly "easier to write code than read it." This is even true of one's own code - returning to something I wrote six months ago, I realised to my regret I left insufficient comments and good names behind - so I had to learn how to understand my own code again, refactoring some of the names once I had worked out what I was doing. But by the same token, if you re-write others' code, there's no guarantee it will be any more readable to the next person - even to yourself, later on. Taking more time to read and understand what the existing code is doing may end up being more valuable. Perhaps one of the problems with this approach is that programmers feel guilty for spending some of their work time 'just reading' other people's code. It doesn't feel like a productive activity in the same way as re-writing. Reading old code just produces understanding in your mind, no tangible output.

  • You don't trust the people who wrote the code.

'Not Invented Here' syndrome. Especially since many programmers have poor code reading skills it's difficult to relax and trust unknown programmers. We can't easily just grok their code and be reassured that it's solid - so fear creeps in and the idea of a complete re-write or making our own version from scratch seems more appealing. If your instinct is not to trust the unknown, it becomes even harder:

"You can’t look down on someone when you read their code. If you don’t respect the person writing the code, you won’t be able to apply the energy needed to understand it." - Keiichi Yano @CaptivNation

In the Python world this has mostly been overcome when dealing with third-party modules - for some reason, if you can pip install a library function to do what you want, there isn't the same need to question and look under the hood in mistrust at how it does what it does. The module is generally treated as a black box, whose documentation is all you need to work with it. Perhaps this trust has been built up in the Python community over time and isn't readily extendable to other domains - it's certainly a large factor in the appeal of Python as a language.

  • It's ugly

And finally the real reason, the one we feel deep-down in our bones: the old code looks bad - it's flaky, it doesn't have any test coverage, the relationship between the parts looks crazy. When you read it, you sometimes want to laugh out loud - it's a big hot mess. There is a strong temptation to start again from scratch out of an aesthetic instinct for perfection.

Why Keep Code?

  • Commercial concerns

Joel Spolsky of Joel on Software fame has called rewriting source code from scratch "the single worst strategic mistake that any software company can make". Spolsky uses the example of Netscape 6.0 to demonstrate why as a corporate strategy, complete re-writes are almost never a good idea. They tend take longer than anticipated (because people are bad at working out how long it will take), and burn time and resources for no appreciable reward until the very end when the new code is ready - by which time, a competitor has probably caught up to you and eaten your lunch. There are almost no commercial examples where a complete re-write turned out to be a good idea. Sometimes as a programmer you need to 'zoom out' and take a more general view of your company's trajectory, and how time spent on re-writes and refactoring fits into it.

Of course, companies also need to take care not to pressure their programmers into behaving in this negative way. If you're rewarded based on new code output or some other metric that doesn't take into account the increase in understanding from reading others' code, it can be hard to fight the instinct to re-write code more than you should. Managers should try to grow their programmers' understanding of the existing codebase and allow time for them to read code as an activity of value in itself. Taking a leaf from Peopleware and accepting that 'human resources' are individuals who are not interchangeable and who contain valuable institutional knowledge should help here.

  • Code learns

As Joel also points out, 'hairy' legacy code functions embody years of bug fixes and reactions to specific situations. But not only that. Legacy code often embodies knowledge about a process, knowledge that is very difficult to recapture. The writers might have left the company, or been run over by a bus! Re-writing doesn't recapture all the nuances of the understanding embedded in the old codebase, and can leave important institutional knowledge behind. This knowledge might not be documented in any other way. I've lost count of the times an old comment or variable name has led me in a valuable direction to a deeper understanding of changes to our hardware, for example. This sort of thing would be lost, throwing the baby out with the bathwater, if the code had been completely re-written by someone who didn't keep the old comments they didn't understand.

  • Refactoring can give the best of both worlds

It can be difficult to get the balance right between too many re-writes on the one hand and leaving flawed, buggy existing code alone on the other. My own experience at CMR has definitely taught me the value of keeping and improving on an existing codebase. Through resisting the temptation to stop and completely re-write parts of the Python codebase, we have come further and faster than we could have done otherwise, and managed to still continue improving as we go along. Refactoring is sometimes used as a synonymn for re-writing, but it's actually a different approach. Refactoring values existing code and makes the base assumption that it is valuable and should be preserved. By adding tests, old code can be refactored with the confidence that bugs won't be introduced. Tweaking variable names and adding explanatory comments is generally harmless and can be very valuable. In this way, incrementally refactoring old code can give excellent results, in less time than a complete rewrite. Your Code as a Crime Scene explains how making improvements to the code can and should be done in a targeted way, rather than by hunches. By focusing on areas with the highest cyclomatic complexity and churn, we direct our energy where it produces the most valuable results. This means the majority of the existing legacy code can be left alone, while still significantly improving the functionality and test coverage.

A Book Recommendation

In the course of my research for this post I came across Code Reading, a book about precisely the discipline reading legacy code in order to maintain it and add features. This looks to be a great primer on a neglected skill for programmers. I plan to read it myself and leave a review here in the New Year.

Oct 30, 2017

PyCon UK 2017!

I spent the last few days at PyCon UK, and thought I'd write a post about my experiences there. It was my first time at the conference and I thoroughly enjoyed it, as you can probably tell from the liberal number of exclamation marks scattered through this post.

I gave a talk!

On the first day of the conference I spoke about Python As a Second Language. The organisers put me in the Biggest Room so I had to fight off some pre-talk nerves, but I was glad to have the chance to do it and got some lovely feedback afterwards. Thanks again to Emma Gordon for encouraging me to give it a go and push my comfort zone! Doing a talk on Thursday also meant I was free to enjoy the rest of the conference without worrying, which I definitely recommend.

For those who are interested, a video of my talk is now up on YouTube!

I went to talks and workshops!

The conference was full of great talks and sessions, so this is just a small sampling of what I particularly remember enjoying. Of course, I'd like to give a shout-out to my colleagues Emma Gordon and Jan Chwiejczak who respectively gave the very silly and fun Python Spelling Bee, and a (very oversubscribed) workshop on Python Bytecode & lavishly illustrated talk on the Art of Testing.

  • Unsafe At Any Speed Rae Knowler made some great points about dangerous library defaults, illustrated with scary examples from the wild. I'll be sure to use PyYAML.safe_load() rather than load() from now on...!

  • Shaping the World David McIver's keyote was thought-provoking and fascinating, not just about software, but ethics, history and human interactions - the sort of thing Stuart Wray would probably enjoy.

  • Docs or it didn't happen! I was encouraged to join the Documentarian Club by Mikey Ariel, who gave an inspiring talk about why good documentation is so important.

  • Software's Seven Deadly Wastes Jez applied the Toyota Production System's 'Seven Wastes' concept to software engineering beautifully - pleasing my manufacturing engineering heart and giving me some food for thought.

  • Circumnavigating the Antarctic with Python and Django A fascinating talk that cast a light on the challenge developing with no (or a very patchy) Internet connection. What, no googling for StackOverflow posts?! Carles and Jen managed data for 22 scientists on a trip circumnavigating the Antarctic, and built them some useful tools as well like an intranet 'Facebook' and web portal to enter their latest data.

  • The micro:bit talks I discovered from the team at the micro:bit foundation how the BBC micro:bit is being used by teachers and for STEM outreach. It's a great project and it sounds like it's already having a lot of success getting kids into learning to code in an accessible way.

  • Choo choo! All aboard the Data Train! It turns out there is a lot of open data available from TfL and National Rail about train movements in the UK. The talk went by quickly but I'll definitely be rewatching to get inspiration for my next project!

  • Lightning Talks One of the highlights of the conference was the range of lightning talks at the end of each day. Among much else they gave me a great brownie recipe, book recommendations and a moment of meditation calm. A particular favourite was the children's lightning talks - they were so confident speaking about their projects, it was lovely to hear.

The nice thing about PyCon UK is that they video all of the talks in the Assembly Room, so I'll be able to go back and watch the ones I missed over the next few weeks, and learn more from the ones I went to.

I didn't take part in many workshops as I was busy manning the CMR stall (we were one of the sponsors so were giving away some free trinkets). I did really enjoy Alex Chan's A Plumber's Guide To Git workshop - I think it really helped unpack the inner workings of Git for me. At the end I started to understand what's going on 'under the hood' when I git add and git commit and it's really neat.

I got swag!


As well as this snazzy pair of Python socks as a thank-you for giving a talk, I also picked up a free BBC micro:bit delightfully packaged in a sweetie-bag and enjoyed playing with it. For such a small bit of kit is has a surprising range of functions, including an accelerometer, 25 LEDs with variable brightness, two buttons and some I/O. I look forward to using it for embedded projects!

I met new people!

One of the best things about PyCon was a chance to meet people using Python from around the UK (and further afield). It was inspiring to see how the language is being used by all sorts of folks. Everyone was friendly and welcoming, and it was a great place to give a talk. I also got the chance to spend more time getting to know people I already was acquainted with from CamPUG, the Cambridge Python Users Group, and had some really interesting discussions.

If anyone is thinking of going but isn't sure if it's for them, I'd really reccomend giving PyCon UK a try - the environment is relaxed and friendly, and the organisers try hard to make everyone feel welcome and included. I'll definitely be coming back next year!

Sep 10, 2017

Why Do We Do This To Ourselves?

Hello! First of all, I'm not dead (for all three loyal followers of this blog!) I got a fantastic new job at Cambridge Medical Robotics as a full-time Python developer, and have consequently had rather less free time for code musings lately. It's been about five months since I first joined and I'm finally starting to emerge from the new-job haze and find my bearings again. In fact, I had time to break my laptop - and fix it again - which is what I wanted to talk about today.

What happened?

I finally found the free time to update my laptop from Ubuntu 12.04 to the latest version of Ubuntu LTS (16.04) a weekend or so ago. I had been seeing the suggestion to update coming up for a while (... nearly a year, it turns out!) and ignoring it. But because I couldn't make a new game run with my old version of Ubuntu without installing a bunch of updates anyway, I finally decided to bite the bullet and do the full upgrade. I'd heard mixed things about how well the transition between versions went for other people, and I was also concerned about keeping my windowing appearance the way I like it, so I knew this would take a while and probably not be straightforward. I backed up my data and even made a list of the useful programs I currently have installed, in case things completely went sideways. What I was hoping not to encounter was ...

Abandon Hope, All Ye Who Enter Here

Anyone who uses an open-source OS will be familiar with this situation. There you are, sitting in front of what was once a beautifully working machine, questioning all your choices and trying to find out how to fix whatever the problem is. The spinal reflex of Linux is the command line. It's what's left when things go wrong. As Neil Stephenson's excellent In The Beginning Was The Command Line reminds us (although here he is actually talking about Windows vs Macs):

"when a Windows machine got into trouble, the old command-line interface would fall down over the GUI like an asbestos fire-curtain sealing off the proscenium of a burning opera. When a Macintosh got into trouble, it would present you with a cartoon of a bomb, which was funny the first time you saw it."

Why even choose Linux?

My motivations

When I got my first laptop as I was about to go to University, I decided to try dual-booting with Ubuntu (it was a Windows machine originally). Mainly it was an experiment - I'd heard that there were some cool coding tools available for Linux systems and I wanted to see what it was like on the other side. I was also kind of a cocky teenager and liked the idea of using a niche, obscure system, customising my laptop in some way. And, most importantly, I had a lot of free time - I took a year out before going to Uni, so aside from working in a gift shop (which didn't occupy my mind that much) I was able to spend time fixing up my laptop the way I wanted. After the inevitable teething problems, I got an installation I was happy with, and enjoyed it so much I ended up just using Ubuntu as my primary system and abandoning the idea of doing dual boot. I kept my system Ubuntu all through college, and though I was sometime concerned I wouldn't be able to complete assignments with it, I was pleasantly surprised by tools such as OpenOffice, which allowed pretty seamless integration with Word, Powerpoint etc. I also had a leg-up on some of my classmates, as when I got to Uni it turned out that the machines in our department all ran Linux installations, too. So I never really had a problem there.

Common fears

But what if there are bugs and I don't know how to fix them? I'm not some l33t hacker!

Returning to In The Beginning Was The Command Line, which really is a stupendous essay, we find a wisdom about bugs which definitely still holds out. Whatever OS you are running will not be perfect. There will be problems from time to time, and you will try to learn how to fix those problems. Neal Stephenson compares the OS situation to a crossroads with different competing auto-dealerships. Customers come there and 90% go straight to the station-wagon dealership (Windows).

The group giving away the free tanks only survives because it is staffed by volunteers, who are lined up at the edge of the street with bullhorns, trying to draw customers' attention to this incredible situation. A typical conversation goes something like this:

Hacker with bullhorn: "Save your money! Accept one of our free tanks! It is invulnerable, and can drive across rocks and swamps at ninety miles an hour while getting a hundred miles to the gallon!"

Prospective station wagon buyer: "I know what you say is true... but ... er... I don't know how to maintain a tank!"

Bullhorn: "You don't know how to maintain a station wagon either!"

Buyer: "But this dealership has mechanics on staff. If something goes wrong with my station wagon, I can take a day off work, bring it here, and pay them to work in it while I sit in the waiting room for hours, listening to elevator music."

Bullhorn: "But if you accept one of our free tanks we will send volunteers to your house to fix it for free while you sleep!"

Buyer: "Stay away from my house, you freak!"'

With an open-source OS like any of the Linux flavours, hundreds of people will be able to help you, and a solution will probably already exist online. StackOverflow and other such repositories of knowledge are great, as are reading the manuals and docs for specific tools you want to use. Whereas proprietary OS vendors are naturally interested in a) Convincing consumers that there are no problems with their product (particularly security problems!) b) Convincing shareholders that their product is commercial (not 'giving anything away for free') and worth paying money for

I don't think I can keep up with the skills you need to run an OS like that

Not going to lie, this can be a barrier. If you're like me and don't enjoy change, the process of continually needing to update and patch your open-source OS can be scary. You ask yourself - what if it doesn't work next time? You think about how you already voided the warranty on your machine by installing this crazy free OS and you question whether you'll be able to fix it.

To this I have several suggestions: - Use an OS which has widespread adoption and is known to be easier to maintain, such as Ubuntu. I began with Ubuntu and continue to stick with it despite some gripes, because the canonical system does make it so easy to install the patches and updates you need to keep rollin'. Plus, the version system means you can go several years without needing to do a major upgrade.

  • Cultivate technically minded friends who can advise if things go very wrong. This can be online or off - Ubuntu has a warm community of volunteers who staff the forums and are generally very helpful and kind to newbies. If you're a student there is often at least one l33t sysadmin in your department who Knows The Ways of Linux and they are generally happy to help - perhaps in trade for chocolate! Depending on where you work your colleagues may be able to help out, too. Linux users tend to be evangelists who want to assist others to enjoy using the systems they do.

  • Comfort yourself by thinking of the various high profile problems with commercial OSes - at least you are not suffering with that!

  • Believe in yourself and your ability to fix things if they go wrong. I can't state this enough! Running my own installation of Ubuntu really helped in giving me the confidence I needed to get into coding and eventually, to get a full-time programming job. You don't have to be an IT professional to run Linux though - people from many walks of life do it for different reasons. One of my friends is a historian who uses Ubuntu to make cross-referenced notes more easily!

  • You don't have to commit to running an open-source OS full-time to give it a whirl and see if it's for you. These days you can fairly easily try booting Ubuntu or Debian from a memory stick. Using a Rasperry Pi will also give you a taste of Linux for a fairly small investment if you already have a separate screen and keyboard. And of course, dual-booting is getting easier to do - meaning you still have a full working installation of Windows alongside your Linux OS should you need or want.

Why continue with it?

For me in particular, it's important to know I have the ultimate control over my machine. As a programmer this is particularly important, since it is the tool of my trade - it's where I go to think and play. But I think the importance of control is true for everyone, if you think about what you use a laptop for. These days your computer contains your life - your bank statements, your music, photos, books, your email history, everything you've touched online. With a commercial OS, you have to admit that you are not the person who ultimately gets to decide what uses your machine can be put to. Whereas with an open-source OS, you call the shots.

Some concrete examples are in order.

I know that I will always fully own my digital books and music. I'm also confident I can make my own content through remixing the work of others, without being prevented from exercising my creativity.

I am a strong believer in the harmfulness of Digital Rights Management. Ultimately in order to enforce this notion (that these things do not 'belong' to you) someone else has to control your means to access them. Lawrence Lessig is far more eloquent than I can be about why it is harmful to lock off access to these things, so I would direct those interested in finding out more to his work which is, naturally, freely available online. I agree with him that the division between 'creator' and 'consumer' is artificial, and ultimately, harmful. I want to pay creators a fair prices for ebooks and music I enjoy, and in return to be freely able to use those purchases whatever way I see fit, just as I would a physical book or a vinyl record - to lend it to a friend, reshape or remix it. One of my hobbies is vidding. This is considered copyright violation of the video and music sources I use, and treated variously depending on my source material - sometimes fond indulgence, sometimes takedown notices and harsh threats. I am confident my OS will never prevent me from making my art, and that no-one else will get to decide what is acceptable for me to work on.

I can control my security and privacy and can be fairly confident that no-one is using my machine against my wishes.

"I just received an e-mail from my daughter, who is very upset, saying, 'Mom, I have my laptop open in my room all the time, even when I'm changing."

This is a big one. People may have heard of the laptops in Philadelphia that spied on schoolchildren and took tens of thousands of pictures of students, teachers and their families at home. The pictures were shared among staff and some were used to discipline students. One student was called into the Principal's office and accused of drug abuse after being secretly photographed eating pill-shaped Mike and Ike candy in his bedroom by his open laptop, for instance.

"[T]here is absolutely no way that the District Tech people are going to monitor students at home.... If we were going to monitor student use at home, we would have stated so. Think about it—why would we do that? There is no purpose. We are not a police state.... There is no way that I would approve or advocate for the monitoring of students at home. I suggest you take a breath and relax." Principal DiMedio in an email to a concerned student intern, 2008

"Among all of the webcam photographs recovered in the investigation there are a number of photographs of males without shirts, and other content that the individuals appearing in the photographs might consider to be of a similarly personal nature." Report of Independent Investigation Regarding Remote Monitoring of Student Laptop Computers by the Lower Merion School District, 2010

During the case, some argued this was fine, because the children didn't really own their laptops - they were issued to them by the school and the families had signed a consent form about the use of "TheftTrack" software. But the same argument can be made for any piece of proprietary software. Do you really read all of those EULAs before you click 'agreed'? If you use the iTunes music store for instance, you'll remember being forced to download a U2 album you weren't interested in and being unable to delete it. You might also remember the irony of Amazon remotely deleting ebook copies of George Orwell's 1984 from people's Kindles. What does your 'ownership' of a piece of proprietary software really mean, when the true owners are the company who created and retain ultimate control over it? Those companies do not necessarily have our best interests at heart.

This is an even bigger issue for those living in repressive regimes which seek to prevent free access to knowledge - Tor and other open-source anonymisation tools and open-source OSs are incredibly valuable to journalists, union organisers, and those working for the cause of human rights and free speech around the globe. The point of open-source tools such as Tor is that anyone is able use them completely freely, even those who the creators rightly despise.

I know that I can completely understand the tools I use, if I take the time to do so. I can even contribute to making those tools better for everyone.

This is a big one as a software developer, but also as someone who enjoys creating works of art. It's liberating to know that, even though I don't understand a great deal of the software I use, I can learn to understand it, and if it goes wrong, I can learn to fix it. The source and config files for Linux are not locked away or hidden. They are just text files that are freely editable - I can eternally change, customise (and definitely break!) my machine if I want. I don't have to stick with the settings that someone else thought would be best for people like me - I can alter how my machine works freely so that it works the way I want. This is particularly great for accessbility features such as screen magnification, audio readers and the ability to navigate without a mouse. The Ubuntu community is definitely ahead of MacOS in accessibility, and Windows to an extent as well.

Warm fuzzies

It's quite nebulous but I do enjoy the sensation of being part of a community committed to helping one another and to continual learning. It's also just fun to feel like I've taken the red pill and decided to understand more about how my machine really works! The thrill of having 'insider knowledge' and feeling a little bit like a hacker, that motivated my teenage self to go and install Linux, never entirely went away for me. Of course, there are sometimes feelings of being a fraud or not knowing enough. But the good outweighs the bad for me. As with other computer-related pursuits, I swing between two states:

Two states of every programmer And I wouldn't have it any other way.

So there you have it. Reasons why I continue to use a Linux OS, despite the sometimes-frustration.

Postscript: what was The Fix?

There's almost no point telling you about what fixed my particular problem, since googling for your specific problem will be far more effective. I've forgotten myself most of the details of what I did. However, if you're really curious, I do keep a notebook for these things (it's a nice way to learn a bit more for next time) so according to my notes, here is what I ended up doing:

  • Pressed 'Shift' as my laptop booted up to access kernel selection and selected my previous happy kernel 3.13 to get into cmd prompt mode.
  • Had a look around using the command line tools at my disposal - this was no hardship since on Ubuntu you can do everything with the command line - it just took me a little while to look up some of the commands. sudo lshw -C Network showed me that network access was disabled - no good if I was going to try installing updates from the internet. sudo service network-manager restart did the trick and got that going again.
  • At first I thought I had a problem with where I was pointing at repositories, so I checked that /etc/apt/sources.list had the sources that a bit of googling led gave me a list of what to expect for 16.04. They were actually fine.
  • I ran a sudo apt-get upgrade and autoclean which seemed to fix some of the errors, but I still saw a message saying dpkg broken.
  • Finally, I found out the fix on this handy bug report - looking in etc/init.d/virtuoso-nepomuk showed me that my file there did indeed miss out a ### END INIT INFO at the end of its block. Using a command-line text editor (since I'm not a l33t Emacs or vim hacker, I just used nano) I fixed that and saved the file. After that, sudo-apt-get update worked. Following a restart, I had a GUI again!
  • After that it was actually relatively simple to get the Gnome interface I know and love back (I really despise the Unity GUI, but that's another post).

That might sound overwhelming - and at the time there were moments of frustration for sure! It took me a few hours, spaced over several days. But I never doubted during this process that my OS problem could be fixed, and that I could be the one to fix it. It helped greatly that I have a tablet, so I was able to go on the internet during the crisis look up suggestions and solutions. These days, smartphones mean most people aren't trapped offline in a situation like this, and can find advice and help.

Apr 18, 2017


'Peopleware' is a surprising book. You pick it up expecting a dry tome about (as the subtitle says) productive projects and teams. I only started to read it on the recommendation of a friend, and I'm so glad I did. It's a classic of software development for a reason. It grips you from the very first page as the authors Tom deMarco and Tim Lister lay out a problem familiar to everyone at work - "politics" - and what can be done about it. Peopleware is by turns scathing, hilarious, and wildly optimistic about making the workplace somewhere that's actually fun to be. It's stuffed with war stories that ring very true to anyone who's been stuck in a dysfunctional work environment. Peopleware is everything you hope a project management book could be, and more. Peopleware even recommends my favourite book of all time, 'A Pattern Language' (I once dreamed of becoming an architect - this book was the wellspring of that desire) as a sourcebook for designing a good work environment. I finished Peopleware in a single delighted afternoon.

My mindmap of Peopleware Here's my mindmap of the first few chapters.

"But Hannah!" you say (and since I'm writing this, I can make you say what I want), "This book was written in the Eighties! It uses COBOL as an example of a modern language! How can I take any of its advice seriously?" To which I would reply, as Peopleware does - You are suffering from the High Tech Illusion, which is:

The widely held conviction among people who deal with any aspect of new technology (as who among us does not?) that they are in an intrinsically high-tech business. They are indulging in the illusion whenever they find themselves explaining at a cocktail party, say, that they are "in computers", or "in telecommunications," or "in electronic funds transfer." Just between us, they usually aren't. The researchers who made fundamental breakthroughs in those areas are in a high-tech business. The rest of us are appliers of their work. We use computers and other new technology components to develop our products or organise our affairs. Because we go about this work in teams and projects and other tightly knit working groups, we are mostly in the human communication business. Our successes stem from good human interactions by all participants in the effort, and our failures stem from poor human interactions.

Even from that small excerpt, you can discern the warm, conversational and down-to-earth style of the book, and the rational sense it makes. Of course it's still relevant today - human interaction hasn't changed very much since the Eighties (or since the dawn of time). It dissects the multifarious ways workplaces can become dysfunctional (beware the Furniture Police!) and then lays out ways to cultivate jelled teams - groups of people excited to work together, who can focus at work, and who create amazing things.

Peopleware is such a good book people are still talking about it, elaborating on it and recommending it today, thirty years after it was written. I discovered after I read it that it's the first book on Joel on Software's Programmer's Bookshelf. Joel says, "I can't recommend this book highly enough. It is the one thing every software manager needs to read... not just once, but once a year." It's also one of Kevin Kelley's 'Cool Tools'. It's that kind of book.

Don't just take my word for it. Go and read Peopleware! It'll be time well spent.

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