Understanding pure functions
A pure function has a couple of important properties: for the same inputs, it produces the same outputs, and it has no side effects (it doesn’t change global variables and doesn’t do I/O). In this recipe, we are going to introduce a few simple examples to make the concept clear. We are mostly – but not exclusively – interested in the second property: the lack of side effects. In later recipes, it will be made clear why pure functions can be quite useful.
We are going to develop a very simple example where we are counting the genes sequenced per sample. We will have a database on a text file with counts for genes. For example, we might have sequenced LCT and TP53 on a sample, and LCT, MRAP2, and POMC on another. The total count would be: TP53: 1, LCT: 2, MRPA2: 1, and POMC: 1. We will be using a CSV file that can be easily read with Pandas or even just the CSV module.
Getting ready
We will be using a simple CSV file...
