YAML Files

As you work with data, you will recognize the need to store it in a structured, reproducible way, known as a file format. There are a great many file formats for different kinds of data.

Here, we must understand YAML, which stands for Yet Another Markup Language. YAML files have the file extension .yml. They are designed to store any kind of data that can be described as:

• name:value pairs, like Wilma:redhead
• lists of values, like Fred, Wilma, Barney, Betty

in a format that is easy to both read and write.

Learn the basics

We won’t give a complete description of the YAML format specifications, which are abundantly covered on the internet:

• https://www.google.com/search?q=YAML+basics

YAML features needed for the MDI

Importantly, the MDI requires only a small subset of all that YAML files can do, which can be summarized as:

• use a colon, “:”, to separate name:value pairs
• use a hyphen, “-“, to enumerate items on a list
• you can create named lists, lists of name:value dictionaries, etc.
• use fixed-width indentation to indicate the level of nesting on an organizational tree

Thus, we get data structures like:

Flintstones:
    People:
        - Fred
        - Wilma
    Pets:
        - name: Dino
          species: dinosaur
Rubbles:
    People:
        - Barney
        - Betty

That’s all we’re going to say! YAML is extremely intuitive, you will quickly understand how to read and write it.

Just remember to choose a fixed-width indentation, either 2 or 4 spaces per your preference, and stick with it.