YAML notes

Concepts

Indentation

• YAML relies on indentation to define nesting levels. Increased indentation indicates a nested element within a list or dictionary.
• Consistent spacing (typically 2 or 4 spaces) is crucial, and mixing tabs and spaces is not allowed.

Lists

• Represented by a hyphen (-) followed by a space at the beginning of each line in the list.
• Order matters in lists, the first element is accessed first

# This defines a list with two elements
  - Element 1
  - Element 2

# This defines a dictionary with two key-value pairs
name: John Doe
age: 30

# Nested element within a list
  - Sublist:
      - Item A
      - Item B

Key-Value Pairs (Mappings)

• Defined with a colon (:) separating the key and value.
• Keys are unique identifiers within a mapping (dictionary-like structure).
• Order generally doesn't matter in mappings.

person:
  name: Alice
  age: 25
  occupation: Programmer

# Accessing the value for key "occupation"
occupation = person["occupation"]

Folding and Literal Scalars

• YAML allows folding long strings (using the > character) to keep the code readable.
• Literal scalars (using | character) preserve newlines and whitespace within the string value.

# Long string with folding (preserves whitespace on the same line)
message: This is a very long message > that would otherwise wrap to the next line 
  but is kept on a single line for readability.

# Literal scalar with newlines preserved
description: |
  This is a description
  with multiple lines
  and preserved whitespace.

Advanced Techniques

• YAML anchors (denoted by &) and aliases (denoted by *) allow referencing and reusing complex data structures within the YAML document.
• While YAML doesn't have arithmetic or comparison operators, it offers these core mechanisms for building and managing data structures.

# Define a base structure with an anchor
base: &common_data
  key1: value1
  key2: value2

# Reuse the base structure with an alias
user1:
  <<: *common_data  # Inherits everything from the base
  username: user_01

user2:
  <<: *common_data  # Reuses the base again
  username: user_02

Data serialization language comparision