YAML Basics

YAML is a human-readable data serializationlanguage that is often used for writing configuration files.

Scalars and Basic Data Types

In YAML, scalars represent simple data types like strings, numbers, booleans, and null. Let's start with these basic data types.

Strings:

Strings are sequences of characters and don't require quotes unless they contain special characters or spaces.

Examples:

name: John Doe
email: john@example.com
message: "Hello, World!"

Numbers:

Numeric values can be integers or floating-point numbers.

Examples:

age: 30
pi: 3.14159

Booleans:

Booleans represent true or false values.

Examples:

is_student: true
has_car: false

Null:

The keyword null represents the absence of a value.

Example:

description: null

Lists and Sequences

Lists in YAML are used to represent sequences of items. Each item is preceded by a hyphen (-) followed by a space.

Lists:

Examples:

fruits:
  - apple
  - banana
  - orange

Nested Lists:

Lists can be nested to create more complex structures.

Example:

people:
  - name: John Doe
    age: 30
  - name: Jane Smith
    age: 25

Dictionaries and Mappings

Dictionaries (also called maps or objects) in YAML use key-value pairs to represent data. Each key-value pair is denoted by a colon (:).

Dictionaries:

Example:

person:
  name: John Doe
  age: 30

Nested Dictionaries:

Dictionaries can be nested to create hierarchical structures.

Example:

user:
  profile:
    name: John Doe
    age: 30

Multi-line Strings and Special Characters

Multi-line strings can be represented using the | character for block literals or > for folded blocks.

Multi-line Strings (Block Literal):

Example:

message: |
  This is a multi-line
  string using a block literal.
  It preserves line breaks.

Multi-line Strings (Folded Block):

Example:

description: >
  This is a folded block
  string. It removes line breaks
  but keeps the content.

Anchors and Aliases

Anchors (&) and aliases (*) allow you to reuse data in multiple places within the YAML file.

Example:

defaults: &default_values
  timeout: 30
  retries: 3

server1:
  <<: *default_values
  host: example.com

server2:
  <<: *default_values
  host: test.com

These are the basics of YAML. With this foundation, you can start writing YAML files and understanding more complex YAML structures used in different applications and frameworks.