Python Core Summit: notes from my talk today

I gave a short talk today about new coders and contributors to developer documentation today. Here are my notes!

Me: Selena Deckelmann Data Architect, Mozilla Major contributor to PostgreSQL, PyLadies organizer in Portland, OR

Focusing on Documentation, Teaching and Outreach

Two main forks of thought around teaching and outreach: 1. Brand new coders: PyLadies, Software Carpentry and University are the main communities represented 2. New contributors to Python & ecosystem

1. Brand new coders: PyLadies, Software Carpentry and University are the main communities represented

(a) Information architecture of the website

Where do you go if you are a teacher or want to teach a workshop? Totally unclear on python.org. Really could use a section on the website for this, microsite.

Version 2 vs 3 is very confusing for new developers. Most workshops default to 2, some workshops now require 3. Maybe mark clearly on all workshops which version. Generally this is a very confusing issue when encountering the site for the first time.

Possible solution: Completely separate “brand new coder” tutorial. Jessica McKellar would like to write this.

(b) Packaging and Installation problems — see earlier long conversation in this meeting about this. Many problems linked to having to compile C code while installing with pip

(c) New coder contribution can come through documenting of issues around install and setup. We could make this easier — maybe direct initial reports to stack overflow, and then float solutions to bugs.python.org

2. New contributors to Python & ecosystem — with a focus on things useful for keeping documentation and tutorials up-to-date and relevant

(a) GNOME Outreach Program for WomenPython is participating!

More people from core should participate as mentors! PSF is funding 2-3 students this cycle, Twisted has participated for a while and had a great experience. This program is great because:

  • Supports code and non-code contribution
  • Developer community seems very cohesive, participants seem to join communities and stick around
  • Strong diversity support
  • Participants don’t have to be students
  • Participants are paid for 3 months
  • Participants come from geographically diverse communities
  • To participate, applicants must submit a patch or provide some other pre-defined contribution before their application is even accepted

Jessica McKellar and Lynn Root are mentors for Python itself. See them for more details about this round! Selena is a coordinator and former mentor for Mozilla’s participation and also available to answer questions.

(b) Write the Docs conference is a python-inspired community around documentation.

(c) Openstack – Anne Gentle & her blog. 3-year participant in OpenStack community and great resource for information about building technical documentation community.

(d) Better tooling for contribution could be a great vector for getting new contributors.

  • Wiki is a place for information to go and die (no clear owners, neglected SEO etc) – Maybe separate documentation repos from core code repos for tutorials
  • carefully consider the approval process – put the people who are most dedicated to maintaining the tutorials in charge of maintaining them

(e) bugs.python.org

Type selection is not relevant to ‘documentation’ errors/fixes. Either remove ‘type’ from the UI or provide relevant types. I recommend removing ‘type’ as a required (or implied required) form field when entering a bug.

The larger issue here is around how we design for contribution of docs:

  • What language do we use in our input systems?
  • What workflow do we expect technical writers to follow to get their contributions included?
  • What is the approval process?

Also see the “tooling for contribution”

PyLadies Meeting notes from “Negotiating the job market: a panel discussion”

Flora Worley organized a fantastic PyLadies PDX meeting called “Negotiating the job market: a panel discussion“.

The meeting was organized in three parts:

  1. Experiences (good, bad and ugly) from four women who entered the software industry in the last 1-2 years.
  2. Managing expectations and setting boundaries from three people, two recent entrants into the industry, and me.
  3. Negotiating the application/interview/offers process (which we turned into a group discussion, led by one panelist)

We kicked things off by asking people to get into groups of four and talk to each other about why they came and what they were hoping to get out of the meeting.

Some of the comments from the meeting and feedback after included:

  • On what was good prep for interviewing: Attending PyLadies and Python User Group meetups to learn new skills, hear about what modules and techniques people are using. (from Amy Boyle, a local developer)
  • Attending PyLadies helped fill in gaps in knowledge useful as a working programmer, even after having a CS degree.
  • “I love being a Pylady, and if it weren’t for this community, I honestly don’t know that I would have continued learning to code.”

Below are my notes from the first panel, anonymized and edited a bit.

How did you find your first job in the industry and know it was the right place for you?

  • I knew a founder of the company from college
  • Knew someone and they invited me to apply. Wrote a great cover letter and got an interview even though they thought I didn’t have the skills for the exact job I applied for.
  • Got the job by going to talks and staying and talking to the speakers.
  • Decided I was more interested in data than my major! Looked around and found a company that was doing a lot with data.

At what point do you say you “know” a programming language?

  • I shy away from saying I “know” something — seems presumptuous to say that the same way it seems weird to say “I’m a writer.” If you’re getting paid to do a thing, though, then you get to call yourself the “thinger”. Coworker has been asking me for help with python and I know the answers to his questions so…
  • Finding ways to help others with things is a good way to boost your confidence.
  • Once I give a talk about something, I have to say I know how to do it because people will come to me for help. It’s a way to force yourself to cram, find out what you know and really don’t know. On my resume I don’t say “I know” — I say “I have experience with XYZ; I have managed to learn these things to get the job done.” Most technical interviews ask more general questions.. not exact syntax of a language.
  • Interviews seem to be trying to figure out if you can learn whatever it happens to be that they need you for at the job.
  • We have to support many languages. So many languages at the same time can get overwhelming.
  • I don’t say I’m an IOS programmer, but I help people write and improve their IOS code all the time.

What was your interview like?

  • Shared projects I made. We just went through my github repo. Tell me about this project, what did you do, what did you use.
  • Was interviewed over Skype
  • Interviewed with 4 people in a marathon. None of those interviews were super technical.
  • The interviews seemed to be gauging whether you would be able to just talk about whatever comes up.
  • They asked me about a lot of command line skills and brought lots of people in from different parts of the company.
  • The interview had me sit down with a program — there’s a bug in this program solve it. What I learned is what matters is the process of how you work on bugs — and being able to communicate that while you’re doing it, not that you actually fix it.
  • Most valued skill is resilience rather than a technical background. You can learn, compensate, fill in gaps. Need willingness to learn, capacity to be frustrated/despair and just move on. People don’t want to hear you freaking out, just want you to do it. Even if it takes you a long time.

Were there classes or resources that prepared you for interviewing?

  • Go out and make something for yourself. Nothing better than finding a thing you want to make, and then making it. Going back to old code, really fulfilling to see progress and wanting to make old code better. You have something to share!
  • Coming to meetings like PyLadies and the Python User Groups. I took some CS classes, but there was lots that I missed. You don’t realize how much you don’t know! Get to meetups to hear about what others are using, what is current in the field. Having a sense of with what the latest stuff is, what are good blogs, best practices, helps out. (seconded by another panelist)
  • Very helpful to go to PyLadies and talk with people around my same experience level. In conversation, people would explain stuff to you in a way that made sense, not just a bunch of jargon.
  • Learning that ecosystem and what tools people use is huge. Helps you figure out what a job entails and what do you need to know to build it.
  • For most of the stuff you’ll build, you’re going to use other libraries. It helps having experience mushing things together. Iterate on it. Every little thing you learn, you’ll find ways of improving stuff.

What if your coding style is really different than other people’s? How do you handle that?

  • Get good at giving constructive feedback
  • “days of spaghetti code is behind us” at the mercy of other people’s crappy code — tech companies deal with this a lot less.
  • Don’t be afraid to say “no idea what this function ” learned a lot about better code by reviewing a lot of code

What kinds of positions can you get? And where do you want to go?

  • Really overwhelming to learn everything I needed to know to support product. It’s an all guys team, learned to love them all, took on a mother role.
  • Teaching stuff all guy team can be intimidating, but most of the guys I work with are college educated CS guys, me having no CS background was intimidating until I realized I knew and could learn this stuff as quickly as they could. No CS didn’t matter.
  • I’m doing tech support, wish I could do more coding. It’s a mixed bag doig support, you learn a lot about system. Found that management wanted everyone to level up in tech support and not go to other parts of the company. I’ve had to come to terms with managers trying to keep me in that role. Need to see how long they expect you to stay in that role before you can move on — ask up front.
  • Had similar experience — resistance to moving from tech support into other roles. Most people in support are looking to move into another role. Make sure you’re on the same page with manager rather than be surprised by it later.
  • On working with guys: my communication style was not really effective when I started. Sometimes had customers that said “can I talk to tech support?” “can I talk to an engineer?”. Had to learn how to be kind of cocky — “This is how this works.” If I was wrong, I was wrong, and had to fix it but that was much more effective at communicating with customers and coworkers.
  • Had to learn that nothing wrong with asking for help. Saves a lot of time.
  • Everything takes me longer than I think it will. Triple your estimates!
  • I needed to learn its ok to ask questions, ask questions confidently rather than despair of never being a programmer. We all tell ourselves crap like: “i’m just generally stupid and can’t learn anything” or “can’t learn javascript in a day, so clearly i’m an idiot”. But turning that around is important for yourself.
  • Be dilligent in the way you ask questions: 1) first google it, stack overflow, check reference book; 2) write out the question fully (rubber ducking) — articulate the problem fully and you might solve it for yourself — what did i expect, what happened, what else can i expect….
  • I’ve had people say to me: “I don’t know why pyladies needs to exist.” I said: “I think its nice its a safe place where that you can articulate your questions without fear.” I don’t know what to do about it other than say that.
  • Men might be made clear to you that they believe we are post-sexist, post-racist. If you have too many of those people around, find a new job.
  • “you need to be careful about where you are” when expressing opinions about feminism.
  • Be open and honest, and they tend to understand.
  • Sometimes it may be the case you have to figure out if an opinion is being expressed because of privilege or malice. If privilege, it can be worked on.
  • Try to internalizing confidence. Tell yourself: “I know how to program” more. Once I really believed that, my programming got better. Because I know I will solve the problem I’m working on!

Do you find that as a woman you communicate differently and you are interpreted differently?

  • Here’s an example: when someone says: “Can you pass the salt?” One person might respond by thinking, “I understand you’re being polite and phrasing that request as a question rather than a command. Sure, here’s the salt!” Or another person might respond with, “I could pass the salt to you. Is that actually what you want me to do?” Pretty different communication styles.
  • Try to be flexible and ride out conflict.
  • I question myself a lot — did i interrupt too many times, was i too aggressive. I worry I am too aggressive.
  • Be yourself. Take time to figure out if you are happy or not.
  • Try to compromise and avoid “truth bombs” where you “explain how the world is”. Take conversations case by case and try not to take it personally.
  • If it gets to be too much, get out of there!

What I mean when I talk about collaboration with teachers: part I

I’ve given a few talks about my experience learning to teach. This is an edited version of my speaking notes for the keynote I gave at the Computer Science Teachers Association conference. This is the best distillation of my thoughts about the value of open source in my life, and what motivates me to contribute and teach. The first half is over 2000 words, so I’m breaking this into two posts. The next part I publish will be the second half of the talk – about the classes I’ve taught, and my lessons learned about what people need to know to get started in free and open source software.

I am a beginner teacher. I’ve only just started writing lessons and teaching classes to adult women who are learning or practicing their programming. All of what I share today is based on my personal experiences working with first time, adult programmers. My plan today is to tell you a little bit about me and what motivates me to teach and contribute to open source, share with you the successes of some of our beginner adult programming efforts and finally what I think open source communities offer teachers.

And I want to start by giving away my punchline. When it comes to working with open source community – of which I’m a member and a leader, and there are many, many leaders without any kind of central authority – I can say for sure today that we’ll come to you.

I’ve been working for the past couple years to find like-minded open source community members, and for those of you in the audience today, I am making a commitment to you – if you want it – to find an open source person to come and talk about what it is that they do to your classroom.

Just contact me (you can leave a comment below – just indicate if you’d prefer I not make your comment public), and I will make this happen, either through Mozilla or through my open source collaborators. I’ve spent the last 16 years going to conferences, and I would like to introduce that network of people to you.

I want to start with something Julie Horvath said recently. She wrote a blog post about women in tech and it struck such a chord with me. The first sentence really stopped me dead in my tracks.

I didn’t grow up thinking I could do anything I wanted to.

When I look at this again, I feel overwhelmed by how much it matches what the women I’ve taught said that they think about programming.

Screen Shot 2013-07-25 at 5.31.27 AM

I see this every time I walk into a classroom to teach beginning programmers. This is a photo from a class on algorithms, people doing a pen and pencil exercise in groups. Several women said afterward they finally felt confident that they could explain what algorithms were. That before coming and working on this in these groups, they literally had never really thought about how algorithms related to programming or what it might mean to implement or create their own algorithms.

I’ve come to think of this as a possibilities problem. People truly have no idea what is possible for them in computer science. And in my teaching experience in particular, many women coming to these classes have a very limited view of what they can accomplish. They don’t know what the job opportunities are, they don’t realize how programming can be used in their lives outside of work, and they know very little about how a computer works or what the main components of a computer are.

When I think about what I really need to do — what my focus is in teaching that I do — I think about changing the scope of what people think is possible. Broadening the scope, and enhancing whatever details I can that make studying programming and ultimately computer science relevant to the lives of the people coming to these classes.

So if we were to just to attach a little overdeveloped importance to this idea of expanding the scope of possibility, we could call this “possibility engineering.”

In my experience, there’s two basic things I have to do – I need to raise awareness, and then I need to offer encouragement. It’s in addition, of course, to teaching real skills that people need. And as classroom teachers, you’re all aware of the need for these two things. I’ve found that these issues are often left out of how outreach and teaching in open source communities is structured.

Screen Shot 2013-07-25 at 5.09.46 AM

This is a picture of a sticky note I drew of how I felt while learning to use a new programming language or trying learn a new module in Python. The top of the graph is “euphoria” or “happiness”, and the bottom of the graph is “despair” or unhappiness. You can see I have a lot of ups and downs!

The peaks are when I’m reading documentation for the first time, succeeding with experiments and implementing code. The valleys are when I actually try the tutorials and they don’t completely work, when I write code that fails and when I’m trying to refactor my test suite. In the end, my emotions level out and if I’m lucky, I end up satisfied with the tool I chose to work with.

Screen Shot 2013-07-25 at 5.11.08 AM

Here’s what I think happens sometimes with the women who come to PyLadies and then never come back. They initially are very happy, but then something happens that causes them to give up.

Screen Shot 2013-07-25 at 5.11.51 AM

In one case, I know exactly what happened — a woman attended the workshops, tried things on their own that didn’t work, and then finally had something break with Python on her Windows laptop and she never came back.

What happens when PyLadies succeeds? What does the emotional graph look like?

Screen Shot 2013-07-25 at 5.12.49 AM

What I’ve seen in the 60+ women that keep coming to meetings is that they continue to have difficult experiences – things break, they don’t know how to fix them.

But they all come back to the group. They ask questions, they commiserate over things that don’t work and they get the help they need to see that they are improving at the same time as they feel as though they are getting better, making friends and being supported. The in-person experiences are key.

Screen Shot 2013-07-25 at 5.13.48 AM

Before we go on, it’s important to acknowledge a key truth about what it is that teachers are teaching. Computer Science is a way of thinking and solving problems. It’s not a company or a product.

This is of course obvious to all of you in this room – but it’s such an important idea to come back to to in all of our work. It’s about getting kids or adults to understand the basics of what a computer is and what it does, and how it stores data about what, where, how and when we do things. We need people to understand these concepts in the same way that we need people to be able to read. When our society is increasingly assisted, augmented and controlled with the help of computers, democracy is at stake when most people have no idea how a computer and software works.

The role of open source groups like PyLadies, of non-profits like Mozilla, is ultimately to empower people: to spread knowledge, dispel myths and invite exploration.

But these groups are mostly helping out people who are already out of high school.

There’s a fair amount of research at this point about what many people think about computers when they’re in high school. I’ve mostly read about what girls think, and try to keep that in mind when I’m advertising my courses. Which brings me to what I thought computer science was all about when I was in high school.

What I knew was:

  • Computers were for playing games
  • Computers were for anti-social boys
  • You’ll find lots of inappropriate, animated ASCII art on computers

And I think that highlights a problem with how we’re collectively handling explaining computer science to the world. We can’t rely on ad-hoc self-education, or discovery learning to help people understand how the whole world is changing.

Screen Shot 2013-07-25 at 5.16.37 AM

Here’s a list of job titles from my colleagues in the industry. Many of these are jobs that didn’t exist 20 years ago, some are jobs that didn’t exist five years ago. So much is changing so fast.

Despite that, we have some real principles – computer science principles – underpinning it all. That’s where we need to focus, while at the same time exposing people to this wealth of possibility.

So, how did I, a person who thought the computers were for gaming, for boys and probably a little bit seedy, get from there to thinking it might be possible to join an open source community and move on to actually changing something I cared about?

In 2000, I made my first contribution to an open source project. I was working at Intel, managing network equipment monitoring and I’d found a problem with how I’d set everything up and needed to modify something like 7000 files to fix it. So I wrote a simple script.

Not too long after that, someone else had a similar problem and posted about it to a mailing list. So I decided, I might as well help that guy out and post the script. Then, I did.

And what happened next totally changed my life. The maintainer of the project not only thanked me, and asked a bunch of questions, he accepted my patch committed it to the main repo, and added me as a contributor to the project’s site.

Mind Blown

I changed the source code of a tool I used every day.

I felt deliciously powerful, so important! And incredulous that something that I’d written that was so obviously terrible, was good enough to be part of a piece of software that I not only used every day, but thought was incredibly great.

And other people used it! I know because I got bug reports later.

Today, I’m a major contributor to the PostgreSQL community, and I founded a chapter of PyLadies in Portland. I’m also deeply involved in many aspects of open source community organizing, like running conferences and helping out with the Ada Initiative. It’s hard to understate how much that patch affected the rest of my life.

I’m super passionate about open source software and I really think collaborating with teachers is awesome. And what I think in particular is great about collaboration between us is getting the open source community to understand teaching at scale. By that, I mean learning how to teach everyone — the way that we teach in our public education system.

Public education is a grand experiment, and a very successful one. Despite the many issues we have with the administration of it, we have a literacy rate that enables us to sustain a democracy and a system for getting an incredible amount of information to most of our republic’s citizens.

We should be using this system to teach everyone about computer science.

Beyond that, I want open source communities to figure out how to teach at that kind of scale. Not only do we need computer science in the classrooms — we need free and open source principles and tools to be taught as well.

We can get there with community members reaching out to teachers as a first step.

And an important part of that is learning what the process of developing lessons and teaching students in classrooms is all about. This is the huge thing we (free and open source developers and community members) can learn from you (teachers).

Teachers and open source community have a lot in common. Some of the more important things are:

  • Minimal resources
  • Teach anyone who shows up
  • Change the world by sharing ideas

My dream in this is that we’ll find a way to provide effective computer science education for everyone.

We’re trying to find that minimal set of concepts that will make people feel empowered at a keyboard, a kiosk or any computer they interact with in their lives. That they understand what’s being said in the newspaper about computers, that they can ask questions without feeling shamed or stupid, and that they can learn more if they choose.

And I don’t mean at all to say that you’re all signing up for teaching everyone. But I am signing up to at least try to do this for the adults in my life that need and want it.

Second half of this talk coming shortly…

What Open Source developers can do for teachers: volunteer to speak in a classroom

I keynoted the Computer Science Teacher’s Association annual conference on July 16th. I gave a talk about how open source developers can help teachers, and what I’ve learned about teaching programming to beginners. The slides are available, although not completely informative about what I said. I plan to write up what I said in that talk after OSCON is finished. Here’s part 1 of the talk.

My pitch to the teachers was: send me an email, and I will find a free and open source community member to give a 15-20 minute talk in your classroom. Lots of teachers are taking me up on it.

To get this done, I set up a form for FOSS community members to provide their contact information. I’ve gotten 163 people as of 8:20am PT July 24. Thanks so much everyone! I know quite a few of the people who have filled out the form, and there are a ton of new people as well. I’m incredibly excited about this. We can all do a lot of good by actually meeting the teachers in our local areas!

Anyone is welcome to sign up, in any location. We have gotten volunteers from every continent except Africa so far.

Most of my teacher contacts are in the US, and I know a few teachers in Germany. If you know teachers who’d like speakers, I’d love to hear from you as well.

I’ve also started a conversation with a few developers about creating an app for connecting teachers and FOSS community members. We’ve got some code in a repo, and a couple people interested in an API for use in some neat remixing applications.

If you’ve got some Django or front-end experience, and you’d like to donate a little time, we’d be happy to have you join us in developing a tool for managing the contact process. I really want the introductions between people to continue to be a “warm handoff”, but it would be nice to remove me as a single-point-of-failure.

I’m setting up a meeting next week. Just ping me either on this post or via email.

A practical guide to using Alembic

I spent some time guiding a coworker through using Alembic for the first time with Socorro this morning and what follows are my notes from that meeting.

I’ve been using Alembic, a database schema migration tool, for about three months now, and really liking it a lot. I created a blog post that served as a slide deck for an internal team called A lightspeed tour of Alembic as my first stab at user education.

Setting things up initially was pretty simple, but explaining it to a coworker after I’d set everything up for myself proved slightly more difficult. Below are my notes on the differences between Alembic and some other migration tool.

Terminology

Alembic calls each migration a revision. Revisions know what order to be run in because each revision is given a down_revision to identify its parent. If down_revision is None, that revision is the very first revision according to Alembic. You can put your whole schema in that revision, or you can just start adding changes to this initial revision. Alembic doesn’t complain either way.

A best practice would likely be putting your entire model into the first revision. I may go back and “fix” this for us later. I opted to just have the default use case be to create a database fresh with a tool we call setupdb_app.py.

If you’re looking to migrate to using alembic, you’ll also need to use SQLAlchemy. I used sqlautocode for my initial schema reflection, and there’s a new tool sqlacodegen you may want to check out for generating your SQLAlchemy models for the first time.

Preparation: edit config and activate a virtualenv

Our environment was set up per the alembic tutorial for creating an environment. I ran:

alembic init alembic

I also put an alembic.ini-dist file into our project’s config/ directory, and modified alembic/env.py to include our model.

To get started working with an existing install, you’ll need to modify alembic.ini-dist, and copy it to config/alembic.ini to fit your environment – setting the connection string and the path to the alembic directory are the two most important settings. We have a script which creates databases from our models.py called setupdb_app.py. This script takes --database_name as a command-line argument. My default for our project is to use breakpad.

We use a virtualenv called socorro-virtualenv. The virtualenv is created automatically if you run make test. If you’re creating a standalone virtualenv, you can do that with virtualenv socorro-virtualenv. Activate this with . socorro-virtualenv/bin/activate.

Creating a revision

  1. Create a fresh database to work from. For Socorro, the command is: PYTHONPATH=. socorro/external/postgresql/setupdb_app.py --database_name=breakpad
  2. Edit models.py with the change to the schema
  3. Run: PYTHONPATH=. alembic -c config/alembic.ini revision -m 'your message about the migration'. The output will include the name of the new file.
  4. Edit the new file as needed alembic/versions/*.py
  5. Run: PYTHONPATH=. alembic -c config/alembic.ini upgrade +1
  6. Test your downgrade with PYTHONPATH=. alembic -c config/alembic.ini downgrade -1

If all goes well, your revision is ready! If something goes wrong, edit and try again. The revision will automatically rollback if there are any errors.

Downgrades are a little tricky to properly execute. In an ideal world, you’d be able to revert the underlying code, but preserve only the commit containing the migration. More on this in a future blog post!

Creating a revision using --autogenerate

This is very similar to the above, with the addition of --autogenerate to your revision command. This should do the right thing, but definitely check your generated file for accuracy.

  1. Create a fresh database to work from. For Socorro, the command is: PYTHONPATH=. socorro/external/postgresql/setupdb_app.py --database_name=breakpad
  2. Edit models.py with the change to the schema
  3. Run: PYTHONPATH=. alembic -c config/alembic.ini revision --autogenerate -m 'your message about the migration'. The output will include the name of the new file.
  4. Edit the new file as needed alembic/versions/*.py
  5. Run: PYTHONPATH=. alembic -c config/alembic.ini upgrade +1
  6. Test your downgrade with PYTHONPATH=. alembic -c config/alembic.ini downgrade -1

If all goes well, your revision is ready! If something goes wrong, edit and try again. The revision will automatically rollback if there are any errors.

Production deployment

You’ll need to deploy an alembic.ini on your production database system and probably a virtualenv to support your python modules.

We deploy our virtualenvs with our application, so this step was pretty simple for everything except for alembic itself. The virtualenv put in full, static paths for the python binaries and had some dependencies that I haven’t figured out yet for actually running alembic. To get around this, I created a virualenv locally on the system for the postgres user. Having your postgres user run the migrations locally is a must for me because I need to access the filesystem to pull in new versions of user defined functions stashed in the directory my model lives in.

I just deploy a new release of our application code on the database server locally, and then I run alembic against the versions directory that’s deployed.

FAQ

And here’s an FAQ for the common problems folks ran into:

OOPS I forgot to create a database before I created a revision!

To “fix” this, try:

  1. Create the database from scratch using your current models.py.
  2. Run: PYTHONPATH=. alembic -c config/alembic.ini downgrade -1
  3. Run: PYTHONPATH=. alembic -c config/alembic.ini upgrade +1

Assuming your downgrade function works, this should allow you reverse the latest revision and then test your migration.

Error message: “Only a single head supported so far.”

See Working with Branches.

I’m using schemas, and alembic doesn’t recognize them when I try to use --autogenerate.

See include_symbol. And be sure to add this to both the “offline” and “online” versions of the revision code in env.py.

Error message: Target database is not up to date.

This means you’ve got a file in your versions directory that contains one or more migrations that haven’t been applied to the current database. You can either apply them with alembic upgrade head or have a look in that directory and remove the migration(s) that you don’t want.

TIL: Formatting, search_path and colorcolumn

The last six months have involved a lot more writing of code than the previous couple of years.

I’ve been tweeting little things I learn on a daily basis and thought I’d look back on this week.

format()

A reocurring problem with report writing is getting numbers formatted properly for the occassion. I discovered ‘format’ in Python this week:

print "{0:.2f}%".format(float(1)/3 * 100)

That prints out a float to 2 decimal places. I looked around and Dive Into Python has similar syntax, but without the format() function. So, the equivalent would be:

print "blah %.2f" % (float(1) / 3 * 100)

So, why use one over the other? A user on StackOverflow suggested that compatibility with 2.5 might drive a person to use ‘%’ over ‘format()’, but otherwise, the poster suggested that format() is the cleaner looking and more flexible choice.

set search_path = bixie

I’m working on a new schema for a project. We’re rolling out a prototype quickly, so we’re going to house it in our existing production database for now. To keep things easy to clean up, Laura suggested that we put things into a separate schema. For managing our database models, I’ve switched to using SQLAlchemy, and also alembic for migrations. This made it super easy to specify that I wanted all the Bixie related tables in their own schema:

class BixieCrash(DeclarativeBase):                                              
    __table_args__ = {'schema': 'bixie'}                                        
    __tablename__ = 'crashes'

And that was it.

Then, to avoid having to add ‘bixie.’ to all the table paths in test queries, I put this command into the tests:

 cursor.execute(""" SET search_path TO bixie """)

I imagine there are some other ways to handle this. We’re not really using the ORM for anything other than schema loading, so I’ll probably add that to our connection initialization code for the new app. Then developers can write their queries as without any concerns about being in the correct schema.

And I’ll glow just a little bit about deploying alembic on stage!

set colorcolumn=80

I’ve been trying to write prettier Python. Today’s micro-effort was figuring out how display a vertical line to tell me when I exceed the 80 character width. The proper command to add to .vimrc is:

:set colorcolumn=80

Which looks something like:

colorcolumn in action

Code review for the new PyLadies in your life

This goes out to all the geeky spouses, partners and friends of brand new programmers:

Code review is a cultural practice.

When you sit down to read the work of another, you bring with you all the experience you’ve had up to that point, the code reviews you’ve received, the mistakes you see yourself making and the bits of hard-won knowledge embedded in your coding personality.

Basically, you bring your coding baggage into your review.

When a brand new programmer shares their code with you, they are fundamentally vulnerable. They’re sharing something creative, and like any new creative endeavor, the product is a newborn taking it’s first few, shaky steps.

They are asking for your help and very likely, they’re asking for an indication that they’ve accomplished something. That all the time they just invested in learning something new — paid off.

And, in the case of PyLadies, women are all stepping out on a limb. Some are taking a Coursera class or maybe a workshop, but mostly working alone. We have each other to learn with and we’re all learning something new. Many people are spending 2 nights a week with a group, and another 15-20 hours a week struggling through the very first programs they’ve ever written.

Here’s the very best thing you can say when a PyLady shares her code with you:

“Thanks for sharing this!”

And then, after you’ve had a look:

“I’ve had a look and you’re doing a great job. Tell me about what you’ve written.”

Seriously. That’s about it.

If the PyLady asks specific questions, give your answers. Keep it short and sweet, and encouraging.

I’m laying this out because lots of the women who are trying this stuff out for the first time have loving, geeky spouses and friends who are very excited that the women in their lives are learning to speak their languages. And some of that enthusiasm comes in the form of detailed critique of style, formatting and design.

I’m here to let you off the hook. Just be encouraging, and ask a few open ended questions. That is all you need to do.

Because the reality is: the PyLady is her own worst critic. And, when she comes to a meetup, she can get the detailed help she needs from the other women who are struggling right along with her.

The people in the group have earned the right to share and receive feedback by strugging together. That’s the value of a cohort and one reason why PyLadies, and groups like them, are so important.

If you’re lucky, you’ll get your chance to share some code back, and maybe even write something together. But you build that coding relationship one encouraging step at a time.

If you’re interested in joining PyLadies-PDX, we’re meeting weekly through December, and then starting Monthly meetings on January.

And, if you want to read more about code review in general, here are some additional blog posts I found useful:

Learning python the hard way: print vs sys.write, and python -u

I knew before that print in Python had some weird properties. Like:

>>> for i in [1, 2, 3, 4]:
... print "blah"
...
blah
blah
blah
blah
>>> for i in [1, 2, 3, 4]:
... print "blah",
...
blah blah blah blah

One thing you’ll notice is that there’s a space between each of the blahs. If you don’t want those spaces, you need to use sys.write. Here’s an example of using sys.write along with a progress bar indicator. Which is exactly what I wanted this for.

Finally, you can indicate to python on the command-line that you want unbuffered stdin and stdout with python -u.

Learning Python the hard way: __init__.py needed for packages (as opposed to modules)

Just ran into this today, and wanted to get it down so I never forget:

Modules are not packages! :)

From the docs, a Module is:

A module is a file containing Python definitions and statements. The file name is the module name with the suffix .py appended. Within a module, the module’s name (as a string) is available as the value of the global variable __name__.

And a Package is:

Packages are a way of structuring Python’s module namespace by using “dotted module names”.

When you create a module and you want other scripts to be able to reference it, you need an __init__.py in the directory containing the modules in order for Python to treat a directory as containing a package.

The error manifests as “ImportError: No module named XXXX”.

All I had to do was touch __init__.py and things worked. I’m sure there are other things I’m going to learn today, but that was a silly one that I didn’t expect, and wasn’t mentioned in the Modules documentation, but is mentioned in Packages.