Yaml Map Vs List

YAML Maps vs Lists: A Quick Guide

YAML uses two fundamental data structures: maps (key/value pairs) and lists (ordered sequences). Understanding the difference is essential for writing clear, structured configuration files.

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📌 1. Maps (Key → Value Pairs)

Maps are like a dictionary in Python or an object in JSON.

• Keys must be unique.
• Values can be strings, numbers, booleans, lists, or other maps.
• Order is usually not important (YAML preserves order, but semantically it doesn’t matter).

Example (YAML):

person:
  name: Alice
  age: 30
  city: Paris

Equivalent (JSON):

{ "person": { "name": "Alice", "age": 30, "city": "Paris" } }

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📌 2. Lists (Ordered Sequences)

Lists are like a list in Python or an array in JSON.

• Defined using a leading - (dash).
• Order matters.
• Items can be strings, numbers, maps, or even other lists.

Example (YAML):

fruits:
  - apple
  - banana
  - cherry

Equivalent (JSON):

{ "fruits": ["apple", "banana", "cherry"] }

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📌 3. Combining Maps and Lists

YAML allows you to nest maps inside lists and vice versa.

Example (YAML):

users:
  - name: Alice
    role: admin
  - name: Bob
    role: user

Here:

• users is a list.
• Each list item is a map with name and role keys.

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✅ Quick Comparison

Feature	Map (Key/Value)	List (Ordered Items)
Structure	Key → Value pairs	Sequence of items
Uniqueness	Keys must be unique	Items can repeat
Order	Not semantically important	Order matters
Access by	Key name	Index number

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👉 In short: Use maps when you need labeled data (like config options), and lists when you need an ordered collection (like a sequence of items).

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