Python Grundlagen (13.5.2020 - 14.5.2020 bei einer Firma in Graz)

Environment

We will try to follow a draft plan, based upon up-front discussion. Please don’t take this as a hard rule - we will take ourselves the freedom to spontaneously go deeper into one topic, at the cost of another.

Unit Testing and Test Driven Development

Part of the requirements was to spend a few words on unit testing and test driven development. I take the opportunity to kind of invert the training scenario, into something that comes into being using the basis of all agile methodologies. Exercises will not have textual descriptions, for example, but will be formulated as unit tests that initially fail (naturally).

Python Installation

The language itself consists of the Python interpreter itself, and a rather complete set of modules (one says, “Python comes with batteries included”). This - the python installation - is the primary focus of this training. We might look into NumPy and/or Pandas a bit.

Note

While the training material covers Python versions 2 and 3, time has come to consider version 2 obsolete.

Please choose Python 3 when installing!

For the matter of this training, for diadactical purposes, I suggest we use the standard Python installation,

  • Download Windows installer from here, and go through the installation process. Take care to check the “add python to path” box.

    (For Linuxers, Python usually comes as part of your favorite distribution and is already installed.)

  • If there is the need to install packages that are not contained in Python’s own set of packages, we will install them using pip.

Data scientists often use a distribution named Anaconda which brings the standard Python installation and a large pre-packaged set of external extensions 1 . If you are already used to Anaconda, then I don’t object.

Programming Environment

As we are all programmers to a certain extent, we know what tools to use. For example, the training does not dictate which IDE (or editor) a participant uses. The exercises are not voluminous enough to justify that, after all; a simple text editor like Nodepad++ is sufficient.

That said, here’s a list of IDEs/editors that are frequently used for Python programming. It is in no particular order, and far from being complete.

  • Visual Studio Code. Not to be confused with Visual Studio, Visual Studio Code is actually a modern text editor, not an IDE. Together with its configurabilty, it can be turned into one, but by itself does not dictate anything upon the user.

  • PyCharm. I frequently see people use it, so it cannot be all that bad.

  • Eclipse and PyDev. Definitely a heavy weight (regarding memory footprint at least) among IDEs, Eclipse knows how to handle Python.

  • Spyder. It is used by data scientists a lot. Running code in it feels like a Jupyter Notebook execution in that there are seemingly strange “cell” like dependencies. (Take this into account when you decide to go with it.)

  • Emacs. (I had to say that.) Your trainer will use it to do occasional live hacking demos. Watching someone use it is ok, but learning how to use it requires a nontrivial amount of patience.

Topics

Day 1: Language Basics

  • Unit testing and Test Driven Development (preparing the basics for the remainder of the training)

  • Very basics: syntax, datatypes, variables

  • Control flow constructs: if, while, for

  • Complex datatypes: list, set, dict

  • Mutability and immutabiliy: tuple

  • Functions and parameter passing

  • Closures

  • Iteration and Generators

Day 2: Advanced Topics

  • More about slicing, and about its use in NumPy

  • Exception handling

  • Modules and packages (“namespaces”)

  • Maybe a larger group exercise, to consolidate news from two days.

Wrap-Up

How Was It?

The training was done online on Zoom, due to the Corona crisis. This was my second online experience (first one is here), and I must say online is not much different from face-to-face. Questions were asked at a normal rate, nobody slept over (at least I did not see anybody falling from their chairs). I would have liked to see faces more, though, and I am definitely missing the off-topic communication during breaks and lunch. All in all, though, I definitely can say that there is no reason to not do trainings online.

That said, we probably tried to squeeze a little too much into only two days. To make the bigger part of the audience more happy, we should have probably explicitly agreed to strip basics (which the plan had dedicated day one to), at the cost of some in the audience who were not so advanced. Such things happen from time to time in trainings, it would appear that it’s the trainer’s job to detect such situations more early. My takeaway is that it is very important to state facts clearly and early, especially in settings where you cannot rely on your nonverbal antennae.

Topics

Being a stubborn greybeard though, I use to insist in bringing big pictures (which Python’s iteration, (im)mutability, and exec() belong to, among others), which I definitely did.

Day two was dedicated to a walk through the unittest module, together with a sketch of what Test Driven Development could do for you. We thereby saw what Python modules and packages are, and how modularization is done in Python. $PYTHONPATH and such. To wrap this up, the sketch ended with a discussion of distutils. We saw what a setup.py file adds, and discussed what (possibly continuous?) integration and deployment is at such a small scale. (Probably Azure DevOps is a rather heavyweight solution to that little local problem; it might solve problems that kept out of reach of this little local training though.)

Later in the afternoon of day two, we were only able to scratch the surface of parallel programming (not among the agreed topics) by discussing how threading is done in Python. We saw how the Global Interpreter Lock (GIL) enables simplicity, but also makes true parallism nearly impossible.

Some topics have only been covered on their surface, others not at all. Clearly two days can’t have it all, so what follows is a list of YouTube links. Opinionated recommendations of mine to expand all those topics that would have been interesting to cover, but which we haven’t had the time for.