Mappings (Dictionaries) 📑¶

Mappings (also known as dictionaries or hash maps) in YAML are collections of key-value pairs. They are essential for representing structured data.

Basic Mappings¶

A basic mapping consists of key-value pairs separated by a colon and space.

yml
person:
  name: chaitu-ycr
  age: 30
  city: chennai 🏙️

person is a key that maps to another mapping.
Inside the person mapping, there are keys (name, age, city) with their respective values.

Nested Mappings¶

Mappings can contain other mappings, creating a nested structure.

yml
company:
  name: ycr Corp
  location:
    city: chennai 🏙️
    state: Tamil Nadu 🛕
  employees:
    - name: chaitu-ycr
      role: Developer 👩‍💻
    - name: ycr dummy
      role: Designer 🎨

company is a mapping with nested mappings for location and employees.
employees is a list of mappings, each representing an employee.

Inline Mappings¶

For simple structures, mappings can be written in a single line using curly braces {}.

yml
address: {street: 123 Main St, city: chennai, zip: 12345}

Inline mapping is a concise way to represent simple key-value pairs.

Complex Keys¶

YAML allows the use of complex types, such as sequences or mappings, as keys. These are enclosed in ? and :.

yml
? [first, second]
: "Tuple as a key"

The key [first, second] is a sequence used as a key for the value "Tuple as a key".

Combining Mappings and Sequences¶

You can combine mappings and sequences to create complex data structures.

yml
project:
  name: Build Website
  tasks:
    - title: Design Layout 🎨
      status: Completed ✅
    - title: Implement Backend 🖥️
      status: In Progress 🔄
    - title: Test Functionality 🧪
      status: Pending ⏳

tasks is a list of mappings, each representing a task with title and status.

Anchors and Aliases¶

Anchors (&) and aliases (*) allow you to reuse values within a YAML document.

yml
defaults: &defaults
  country: INDIA in
  currency: RUPEE 💵

location1:
  <<: *defaults
  city: chennai 🏙️

location2:
  <<: *defaults
  city: Pondicherry 🌴

defaults is an anchor that can be reused in other mappings using <<: and *