A Quick Introduction to YAML

Introduction

YAML is a simple human readable language to represent data. YAML stands for " YAML Ain't Markup Language". Previously it was known as "Yet Another Markup Language".

But, It is neither a programming language nor a markup language, It is actually a Data Serialization Language.

YAML is used to store information about different things, we can use YAML to define key-value pairs things variables, list, objects.
YAML is very similar to another language called JSON (Javascript Object Notation), but YAML emphasis on Readability and user friendliness like super readable and super clean.
We can define YAML files in two different extensions .yaml or .yml.
The --- symbol mark represents the start of a yaml document.
The ... symbol mark represents the end of a yaml document.

Data Serialization

Data Serialization is is the process of converting a data object into a byte stream that can be used to store, transfer and distribute on physical devices.
The reverse process of Data Serialization is know as Data Deserialization.
Examples of Data Serialization Languages: YAML, XML, JSON

Comment in YAML

There is no multiline comment in YAML, only Single line comment.

# This is a comment

Data Types in YAML

String

We can define a Strings in 3 ways:

# String Datatype
firstName: "Sanyasee"
lastName: 'Sahu'
occupation: Software Developer

# we can specify the type also
message: !!str "Hello! How are you?"

Numbers

We can directly use numbers (YAML will automatically detects it) or we can specify the type also.

# Numbers

age: 24
cgpa: 8.26
favNumber: 1e+10 # Exponential value


# specify the type 

number: !!int 17
commaValue: !!int 1_54_000  # 1,54,000
mark: !!float 90.50

Booleans

Booleans are True/False Values.

# Booleans

male : true
sleepy: false

Dates

All dates & date times inside YAML are gonna be defined using the ISO 8601 Standard.

# Dates

birthDay: 1998-06-14 09:10:20   # ISO 8601

Null Value

# Null value
flaws: null

Objects

We can store all these values into an object, using indentation (space).

# Store all informations into an Object

person: 
  firstName: "Sanyasee"
  lastName: 'Sahu'
  occupation: Software Developer
  age: 24
  cgpa: 8.26
  favNumber: 1e+10
  male : true
  birthDay: 1998-06-14 09:10:20
  flaws: null

Lists

We can store a list of items.
Each item in the list is gonna be using dash (-) which will indicate it is an item in the list.

  # Lists in YAML

  hobbies:
    - movies
    - riding bike

  # Another notation 
  movies: ["A Beautiful Mind", "The Pursuit of Happyness", "Dark Knight"]

  # Complex List like List of Objects
  # Each entry in this list will be an object
  friends: 
    # Way 1
    - name: "Udit"
      age: 25

    # Way 2
    - {name: "Sagar", age: 24}

    # Way 3 : Easier to read
    - 
      name: "Gajendra"
      age: 25

Multiline & Formatted Information

We can store information in multiple line which in easy to read and considered as a single line.
We can also preserve the format of the information.

# Multiple Lines & Formatted Information

# Writing Information in mupliple lines for readability but as a single line

  # Consider as a single line
  bio: >
    I am Software Developer
    from India,
    and I like tea.

  # Preserves the formatting of the data
  signature: |
    Sanyasee Sahu
    Software Developer
    Email- sanyasee12@gmail.com

Anchoring

Anchor a value and access it in other places in the yaml file.
An anchor does not have to match the key.
We can define an anchor by (&) and access it by (*).
We can also anchor an entire key-value pair.

# Anchoring
person: 
  firstName: &name "Sanyasee"
  lastName: 'Sahu'
  occupation: Software Developer

  id: *name

  # Anchoring enitre key-value pair
  base: &base
    var1: value1

  foo:
    <<: *base       # var1: value1
    var2: value2

Other Data Serialization Languages

Let's take a same piece of information and represent it using YAML, JSON & XML.

YAML

Peoples: 
  - name: "Sanyasee Sahu"
    age: 24
    occupation: "Software Developer"
    company: "HashedIn by Deloitte"

JSON

{
    "Peoples": [
        {
            "name": "Sanyasee Sahu",
            "age": 24,
            "occupation": "Software Developer",
            "company": "HashedIn by Deloitte"
        }
    ]
}

XML

<Peoples>
    <name>Sanyasee Sahu</name>
    <age>24</age>
    <occupation>Software Developer</occupation>
    <company>HashedIn by Deloitte</company>
</Peoples>

Source Code & Converter Links

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