Using Python ipdb from Jupyter

If we try to use the usual ipdb commands from a Jupyter (IPython notebook)

we will get a similar error:

The solution is to use Tracer instead:

Source: http://stackoverflow.com/questions/35613249/using-ipdb-to-debug-python-code-in-one-cell-jupyter-or-ipython

How to publish a Python package to PyPI

PyPI is the Python Package Index, that archive that let you install a package using pip, for example: pip install Flask

In the past days I started writing a Python API client for Toshl expense manager and I decided to publish the library on PyPI. You can have a look at my library here https://github.com/andreagrandi/toshl-python (please note: it’s still in development and Toshl API is not even public yet) in case you are not sure how to structure it.

I found a nice guide but it wasn’t complete (for example it didn’t say how to sign packages) so I decided to rewrite it adding more information.

Create PyPI accounts

To publish packages on PyPI you need to create two accounts: one for the production server and another one for the test server. When you register, please specify (if you have one, but I really hope you do) the PGP id of your public key. Once the accounts are created, you need to create a file named .pypirc in your $HOME folder containing the following configuration:

Please substitute your_username and your_password with the details you sent during the registration.

Preparing the package

I assume you have structured your library in the proper way and have included a setup.py with all the configuration (it’s not something specific to PyPI so you should have done it already). If you haven’t I remember you can give a look at my library here https://github.com/andreagrandi/toshl-python in particular to the setup.py:

Upload the package to PyPI Test server

The first time you upload the package you will need to register it:

and then you will need to build the package and upload it (please note I’m using the –sign to sign the package with PGP):

Upload the package to PyPI production server

Once you have verified that you are able to build and upload the package to the test server (without getting any errors), you should upload it to the production server:

This is everything you need to do if you want to publish a Python package on PyPI. Happy coding!

Using a light sensor with BBC micro:bit and MicroPython

A light sensor is a small component with a particular characteristic: it is basically a resistor and its resistance decreases if the light is more intense. To use it with micro:bit we need to use one of the analogic ports. To build this circuit you will need a breadboard, 3 jumper wires, a 10k resistance and possibly a Kitronik breadboard kit.

The project

I wanted to realise a simple project where, depending on the light intensity captured by the light sensor, the micro:bit shows an image of the Sun if the light is intense and an image of the Moon if the light is less intense.

Here is the complete circuit scheme:

microbit_breadboard_schema_light

“Image Copyright © Kitronik”

 

and here is a picture of the finished project I created:

microbit_breadboard_example_2

The source code I needed is available here:

and as a demo I realised this small video:

Prototyping BBC micro:bit projects with Kitronik breadboard kit

BBC micro:bit has a few IO pins that can be used to interact with external devices. The problem with the board is that it’s not easy to connect the classic jumper wires (those that we normally connect to a breadboard) to the micro:bit, unless using a crocodile clip and being limited to just 3 pins.

Kitronik breadboard kit solves this problem, offering an interface where the micro:bit can be plugged and all the pins are easily connectable to the breadboard using normal male/female jumper wires.

I’ve built a very simple circuit following an example you can find on this manual https://www.kitronik.co.uk/pdf/5603_inventors_kit_for_the_bbc_microbit_tutorial_book.pdf

microbit_breadboard_example_1

To build the circuit you also need 4 male/female jumper wires and two buttons. All this circuit does is to connect the buttons to the micro:bit pins that relate to those buttons. Basically pressing those buttons is the same as pressing button A or button B on the micro:bit board. Here you can see the schema in detail:

Screenshot 2016-02-07 14.30.36

“Image Copyright © Kitronik”

I’ve also made a short video so that you can see it in action:

And of course the source code is available too:

Using BBC MicroBit accelerometer with Python

In these days I’m having a bit of fun with BBC MicroBit board and I’m learning how to use the different sensors available. The latest one I wanted to try was the accelerometer. The board can “sense” if you are moving it in any of the 3 dimensional axes: X, Y, Z. According to the documentation there are four methods available that can be used to get these values: microbit.accelerometer.get_values() will return you a tuple with all the 3 values, while microbit.accelerometer.get_x()microbit.accelerometer.get_y()microbit.accelerometer.get_z() will give you the single values.

The documentation on the official website doesn’t explain much and for example I didn’t even know what was the range of the values I can get back from these methods (by the way it’s between -1024 and 1024), so I decided to play with the code directly and write a very simple example. The small example I wrote, shows a smile on the board display if you keep it straight and shows a sad face if you bend it. This is the result:

and this is all the needed code of the application:

In the next days I will try to play with more sensors and to publish other examples.