Introduction
In the next 2 following articles, we will see together how YAML Files are created to store data and how we can retrieve data from them.
It will be useful in a lot of my incoming articles (i.e Kubernetes series (!))
YAML (“YAML Ain’t Markup Language”) is a human-readable data-serialization language.
It is less complex and ungainly than XML or JSON, but provides similar capabilities. It essentially allows you to provide powerful configuration settings, without having to learn a more complex code type like CSS, JavaScript, and PHP.
Here are the following basic rules YAML has in place to avoid issues related to ambiguity in relation to various languages and editing programs :
- YAML files should end in .yaml whenever possible in Grav.
- YAML is case sensitive.
- YAML does not allow the use of tabs. Spaces are used instead as tabs are not universally supported.
A cheat sheet and full specification are available at the official site : Here
Understand YAML Files
If you have already worked with XML or JSON, you will easily pick it up. If not, in my opinion the best way to understand how it works is through exercices.
A YAML file is basically used to store data. And even in YAML, you have multiple ways to store date.
How to store data in a YAML File
Key Value Pair
The first way to store data is to use a Key Value Pair like so :
Car: Audi Fruit: Apple Animal: Alligator
You can see that the keys (“Fruit”, “Car” and “Animal”) are separated by a colon to their values (“Audi”, “Apple”, “Alligator”). It’s important to have a space after the colon !
Arrays / Lists
Here is how you can store arrays in a YAML File :
Car: - Alpha Romeo - Audi Fruit: - Apple - Apricot Animal: - Alligator - Alpaca
It’s pretty easy as you can see. Just notice that the dash means that the Element is an Array.
Dictionaries
A dictionary is a set of properties grouped together.
Car: Brand: Audi Model: A3 Color: Black
Here we try to represent all information we have on a specific car. Notice the blank space before each items. You must have equals number of blank spaces.
Mixed data
We can have multiple ways combined together to store our data. Like lists containing dictionnaries containing lists.
Here we have a list of cars and the elements of the lists are “Audi” and “BMW” but each of these elements are dictionnaries containing information on the specified car :
Cars: - Audi: Owner: John Doe Model: A3 Color: Black - BMW: Owner: Jane Doe Model: A3 Color: Black
When do we I need to use a dictionary or a list ?
First of all, it is important to understand that YAML files are used to store data. It could be data about anything.
If we continue to take as an example, “cars”, the best way to store informations on it is a dictionary. We can store all information we want (“owner”, “color”, “model”, “price” etc) :
Car: Brand: Audi Model: A3 Color: Black Owner: John Doe Price: $40,000
However if we want to split information like the owner into different parameters like the “familiy name”, the “age” or the “firstname”, dictionnaries won’t be enough. We will use a dictionary in our previous dictionary :
Car: Brand: Audi Model: A3 Color: Black Owner: FamilyName: Doe FirstName: John Age: 33 Price: $40,000
Now, imagine that we want to store 3 cars, with 3 different owners. The best way to do that is to use a list of dictionaries like so :
- Car1: Brand: Audi Model: A3 Color: Black Owner: FamilyName: Doe FirstName: John Age: 33 Price: $40,000 - Car2: Brand: BMW Model: Z3 Color: White Owner: FamilyName: Doe FirstName: Jane Age: 28 Price: $50,000 - Car3: Brand: Tesla Model: Model 3 Color: Blue Owner: FamilyName: Morgan FirstName: Dexter Age: 35 Price: $60,000
Important Note
- Dictionaries are unordered !
- Lists or Arrays are ordered !
That’s all, I hope it will give you enough tips to be able to read or write YAML files easily.
In the next article, we will see together JSON files. It will be easy to understand as you know how to read YAML files.
We will also see together how we can retrieve data from it ! 🙂
Sources :
wikipedia
yaml.org
