How to host private Python packages on Bitbucket for free, AND how to use them in a circleci pipeline

Bitbucket is great for hosting private git repos. Turns out, it can also be used to turn those repos into python packages that you can integrate into your projects with pip. This took a bit of trial and effort to make happen, let me know if there is anything additional you had to do to get things working on your end and I can add them to the guide.

Background

This whole process is built on pip’s ability to install packages from common VCS’s using SSH keys for access credentials. The syntax for doing that looks like this:

Pretty slick, you can even specify a branch or tag:

Since this repo is public, let’s try installing the package into a python virtual environment:

No dice. It didn’t work because our development environment isn’t configured correctly. Let’s get started with the guide.

Using private repo packages locally

Note: I’m on ubuntu 18.04, but I will leave Windows notes in each step if applicable.

Step 1: Make sure your repo CAN be installed as a python package

The key here is a proper setup.py file. Here are best the best set of docs I’ve found on how to make this file.
 
You can also look at the test repo for this project (https://bitbucket.org/esologic/sample_project/src/master/), it contains an example setup.py. This repo will also be the standard example for this post.
 
To make sure things are working correctly, you can try installing the package into your local python environment, or into a virtual one like I’m doing. Using sample_project as an example, we can do this like so:

If your package behaves as expected when installed like this locally, you’re all set to push the changes to your bitbucket repo and continue with the rest of the guide.

Step 2: Create SSH keys and add them to bitbucket

Note: at a few places in this step I use my own email as a reference, dev@esologic.com. Make sure whenever you see that, to substitute email address associated with your bitbucket account.
 
If you already have ssh keys created on your computer or whatever you’re developing on, they should be located at ~/.ssh. If you don’t see both id_rsa and id_rsa.pub files in that directory, create them with:

Leave passphrase blank.
 
Now, copy the contents of ~/.ssh/id_rsa.pub to bitbucket. The following images should walk you through the steps, make sure to give the key a memorable name.
Now, the ssh key of whatever dev environment you’re on is added to bitbucket.

Windows steps to create ssh keys

I followed these two (1, 2) guides to create ssh keys on windows.
The short version goes something like this:

Then follow the step above to add the keys to your bitbucket account.

Step 3: Make sure your account can read from the private repo with your python package

This is a simple, but a trap for young players. Make sure the account you’re trying to install the module with has at least read settings on the repo.

Since the Devon account is an owner of the repo, it will be allowed to read from the repo. The account ci_bot will also be able to read from the repo because it has read permissions.

Step 4: Install the package from bitbucket

With the bitbucket repo permissions set, and your SSH key added to your bitbucket account, you should be able to re-run the installation command from earlier and use the package.

Fantastic! Remember, your pip command git+ssh://git@bitbucket.org/esologic/sample_project.git will be different for your package. It will look something like this: git+ssh://git@bitbucket.org/{your username}/{your project}.git.

Any user that you give read permissions to on the repo will be able to install your package as well. This includes a machine user, so your CI builds can use your private package as well, which I’ll show you how to do next.

Using private repo packages in circleci

Bitbucket and circleci go together like peanut butter and chocolate. Adding CI to a bitbucket project is made fast and easy using circleci.

Step 5: Create a “machine user” in bitbucket

This user should have read only access to the package repo that you want to add to ci, so in this example it’s the sample_project repo.
 
You can accomplish this very easy through the BB ui, just make sure to keep track of whatever username and password you decide on.
 
Just to be clear, a machine user is just a regular bitbucket user that is only used by machines.

Step 6: Create SSH keys and add them to your machine user’s account

On whatever you system you have been using so far, enter the following commands and remember to leave passphrase blank.

Add the contents of ~/.ssh/ci_bot_keys/id_rsa.pub to bitbucket while signed in as your machine user like we did in step 2.

Step 7: Try git+ssh key insertion locally

(Note: you can skip this step, but if things don’t work when you add the step to your CI build start looking for errors here.)

By setting the environment variable GIT_SSH_COMMAND you can select which SSH key gets used by pip when doing an ssh pull.
 
Let’s try out the concept, and try out our new key locally. Run these two commands:

And then install your project like you did before. The package should install no problem, and you should see the same output as step 4.

Step 8: Set the $KEY environment variable in circleci

We now want to make the private key we made for our ci bot (~/.ssh/ci_bot_keys/id_rsa) available to the circle build process.
The only tricky part here is that the private key will contain newlines. For simplicity, we can replace them with underscores, and add the newlines back in the circle build.
 
Copy the output of this command to your clipboard:

The output ends after -----END RSA PRIVATE KEY-----_ in case your terminal doesn’t wrap correctly.
 
Now we need to set this value to the env var $KEY in the circleci build that we are trying to use our private package (sample_project) in.
 
Click the gear on the project page for your project in circle. For me, this brought me to https://circleci.com/bb/esologic/crossbow/edit, where crossbow is the name of my project.
 
Go to build settings -> Environment Variables and then set the variable like so:
 

Now that the variable is set, we need to change our circle config to use it.

Step 9: Add the step to your /.circleci/config.yml file

This does the same thing that we just tried locally, but in circle.
Make sure to put this step BEFORE the step that installs your python dependencies.

Make sure you select a circle image that has a git version of 2.17.0 or later, or this step will fail without an explanation. I found that the python image of circleci/python:3.7-buster worked when testing.

Try running your job, with this step added, it should be able to pull the package from your private repo. Let me know if you run into issues and I can try to help you out. Maybe donate the money you saved on hosting fees to me via paypal? 🤷💖

Thanks to

  • http://redgreenrepeat.com/2018/05/25/specifying-different-ssh-key-for-git/

Play multiple sound files on multiple output devices with Python and sounddevice

Ever wanted to have multiple different sound files playing on different output devices attached to a host computer? Say you’re writing a DJing application where you want one mix for headphones and one for the speakers. Or you’re doing some sort of kiosk or art installation where you have many sets of speakers that need to all be playing their own sound file but the whole thing needs to be synchronized. This would even be cool for something like an escape room.

The ladder example is where I needed this bit of code. I’ve been working with interdisciplinary artist Sara Dittrich on a few projects recently and she asked if I could come up with a way to play 8 different mono sound files on 8 different loudspeakers. Here’s a video of the whole setup in action, and an explanation of the project:

I’ve wrapped up all of the code for the art installation project, and that can be found in a github repo here. It includes the startup functionality etc. If you’re interested in recreating the video above, that repo would be a good starting place. The following is a list of the parts used to make that build happen:

Multi-Audio Example

It is worth it to give a simple example of how to play multiple files on multiple audio devices using python. I couldn’t find an examples on how to do this online and had to spend some time experimenting to make it all come together. Hopefully this saves you the trouble.

To install sounddevice on my Raspberry Pi, I had to run the following commands:

For this example, let’s say there are 4 audio files in the same directory as multi.py , so the directory looks like this:

The code is based on the sounddevice library for python, whose documentation is pretty sparse. This script will find the audio files, and then play them on as many devices as there are attached. For example, if you have 3 sound devices it will play 1.wav, 2.wav and 3.wav on devices 1-3. If you have any questions, feel free to ask:

Here are some more photos of the build:

Why you should use Processes instead of Threads to isolate loads in Python

Key Learning

Python uses a Global Interpreter Lock to make sure that  memory shared between threads isn’t corrupted. This is a design choice of the language that has it’s pros and cons. One of these cons is that in multi-threaded applications where at least one  thread applies a large load to the CPU, all other threads will slow down as well.

For multi-threaded Python applications that are at least somewhat time-sensitive, you should use Processes over Threads.

Experiment

I wrote a simple python script to show this phenomenon. Let’s take a look.

The core is this increment function. It takes in a Value and then sets it over and over, increment each loop, until the running_flag is set to false. The value of count_value is what is graphed later on, and is the measure of how fast things are going.

The other important bit is the load function:

Like incrementload is the target of a thread or process. The z variable quickly becomes large and computing the loop becomes difficult quickly.

The rest of the code is just a way to have different combinations of increment and load running at the same time for varying amounts of time.

Result

The graph really tells the story. Without the load thread running, the process and thread versions of increment run at essentially the same rate. When the load thread is running, increment  in a thread grinds to a halt compared to the process which is unaffected.

That’s all! I’ve pasted the full source below so you can try the experiment yourself.

Raspberry Pi Digital Hourglass

Trying to get the most out of a day has been big theme of my life lately, as I’m sure it is for many people. I’ve found that I always manage my time better when things are urgent; I’m considerably more productive when I have to be.

I want an ascetically pleasing way to be able to represent how much time is left in the day at a granular scale, like an hourglass. Watching individual seconds disappear will look cool and (hopefully) create that sense of urgency that I want to induce.

Technically, this is a really simple thing to accomplish thanks to python and pygame. Here’s a video of a proof of concept running on my laptop:

At the start of each day, the display is filled with squares at random locations, with a random color. As each second elapses, a square will vanish.

To make it easier to see for the video, I’ve made the squares much bigger than they will actually be for the final build. This is what the display looks like with the squares at their actual size:

The code really really simple, like less than 100 lines simple. Here’s how it works:

Here’s the version of the code running on my computer in the video:

Let’s walk through some of the design decisions of this code. The first thing that’s worth talking about is how the data for the squares is handled:

It’s just an object with no methods, and on initialization, all the parameters of the square (location and color) are generated randomly as opposed to just floating the raw numbers in arrays around (even though that’s basically what is happening). This let’s us fill the squares array very easily later on in the file here:

and here:

When it comes time to draw these squares, it also makes that pretty intuitive:

Again, very simple stuff, but worth it to talk about.

I’ll be back at my place that has the Raspberry Pi and display I would like to use for this project, so more on this then.

Thanks for reading!

PiPlanter 2 | Solving Broken Pipe Errors [Errno 32] in Tweepy

If I haven’t mentioned it already, https://twitter.com/piplanter_bot IS the new twitter account for PiPlanter. Like last time, I’m using the tweepy library for python to handle all things twitter for the project. What I’m NOT using this time is Flickr. From a design point of view, it wasn’t worth it. It was too complicated and had too many things that could go wrong for me to continue using it. Twitter is more than capable of hosting images, and tweepy has a very simple method of passing these images to twitter. Recently I moved the whole setup indoors and mounted it all onto a shelf seen here and it came with a set of strange problems.

Long story short, what I think happened was that since I moved them to a different location, the complexity of the images increased, causing an increase in the size of the images themselves. A broken pipe error implies that the entirety of the package sent to twitter wasn’t sent, causing the tweet not to go through. I first started to suspect this problem after seeing this:

 

The graphs were going through just fine, but images were seeming to have a hard time. You can’t tell from this photo, but those tweets are hours apart as opposed to the 20 minutes they are supposed to be. Once I started having this problem, I bit the bullet and integrated logging into my project which produced this log:

Hours and hours of failed tweets due to “[Errno 32] Broken pipe”. I tried a lot of things, I figured out that it was the size of the images after seeing this:

Photos that were simple in nature had no problem being sent. After scaling the image size down, I’ve had absolutely no problem sending tweets.


If you are tweeting images with tweepy in python and getting intermediate Broken pipe errors, decrease the size of your image.
Thanks for reading.

Hey! This post was written a long time ago, but I'm leaving it up on the off-chance it may help someone, but proceed with caution. It may not be a good idea to blindly integrate this code or work into your project, but instead use it as a starting point.

PiPlanter | Bringing most of it together

Last night I finished the majority of the software for this project. Here’s a video of me going over what happened and what the program does in simpler terms:

Essentially, every hour, the raspberry pi samples data from 4 humidity probes, an LDR and a tmp sensor. Once the sampling is complete, it dumps the data into a mysql database. From there the data is rendered into a graph using pChart in the form of a .png image. From there, that .png files is uploaded to flickr using this api. Once the file is uploaded, it returns it’s photo ID to the python script. From there, a tweet is built containing the brightness at the time of the tweet, the temperature at the time of the tweet, and the average moisture of the plants. It also uses the photo ID from flickr obtained earlier to build a URL leading to that image on flickr which it tweets as well. The final part of the tweet is a url that leads to this post!

That was a lot of explanation, but this program does quite a bit. The source comes in two parts, here’s the python script that handles the brunt of the processing. You will need a bunch of libraries to run this, you could pick through past posts of mine to find what those are, but when I do a final post for this project I will include all of those.

Here’s the .php script that renders the graph from the mysql data. It is called by the python script.

Thanks for reading!

Hey! This post was written a long time ago, but I'm leaving it up on the off-chance it may help someone, but proceed with caution. It may not be a good idea to blindly integrate this code or work into your project, but instead use it as a starting point.