YAML Cheat Sheet

YAML
Cheat

YAML Basics

Scalar types


n1: 1            # integer          
n2: 1.234        # float      

s1: 'abc'        # string
s2: "abc"        # string
s3: abc          # string

b: false         # boolean type

d: 2015-04-05    # date type

Variables


some_thing: &VAR_NAME foobar
other_thing: *VAR_NAME

Comments


# A single line comment example

# block level comment example
# comment line 1
# comment line 2
# comment line 3

Multiline strings


description: |
  hello
  world

Inheritance


parent: &defaults
  a: 2
  b: 3

child:
  <<: *defaults
  b: 4

Reference


values: &ref
  - Will be
  - reused below
  
other_values:
  i_am_ref: *ref

Folded strings


description: >
  hello
  world

Two Documents


---
document: this is doc 1
---
document: this is doc 2

YAML uses --- to separate directives from document content.

YAML Collections

Sequence


- Mark McGwire
- Sammy Sosa
- Ken Griffey

Mapping


hr:  65       # Home runs
avg: 0.278    # Batting average
rbi: 147      # Runs Batted In

Mapping to Sequences


attributes:
  - a1
  - a2
methods: [getter, setter]

Sequence of Mappings


children:
  - name: Jimmy Smith
    age: 15
  - name: Jimmy Smith
    age: 15
  -
    name: Sammy Sosa
    age: 12

Mapping of Mappings


Mark McGwire: {hr: 65, avg: 0.278}
Sammy Sosa: {
    hr: 63,
    avg: 0.288
  }

Sequence of Sequences


my_sequences:
  - [1, 2, 3]
  - [4, 5, 6]
  -  
    - 7
    - 8
    - 9
    - 0

Nested Collections


Jack:
  id: 1
  name: Franc
  salary: 25000
  hobby:
    - a
    - b
  location: {country: "A", city: "A-A"}

Unordered Sets


set1: !!set
  ? one
  ? two
set2: !!set {'one', "two"}

Sets are represented as a Mapping where each key is associated with a null value

Ordered Mappings


ordered: !!omap
- Mark McGwire: 65
- Sammy Sosa: 63
- Ken Griffy: 58

YAML Reference

Terms

Sequences aka arrays or lists
Scalars aka strings or numbers
Mappings aka hashes or dictionaries
Based on the YAML.org refcard.

More types

!!set

{cherries, plums, apples}

!!omap

[one: 1, two: 2]

Tag Property (usually unspecified)

none

Unspecified tag (automatically resolved by application)

Non-specific tag (by default, !!map/!!seq/!!str)

!foo

Primary (by convention, means a local !foo tag)

!!foo

Secondary (by convention, means tag:yaml.org,2002:foo)

!h!foo

Requires %TAG !h! (and then means foo)

Verbatim tag (always means foo)

Language Independent Scalar Types

{~, null}

Null (no value).

[1234, 0x4D2, 02333]

[Decimal int, Hexadecimal int, Octal int]

[1_230.15, 12.3015e+02]

[Fixed float, Exponential float]

[.inf, -.Inf, .NAN]

[Infinity (float), Negative, Not a number]

{Y, true, Yes, ON}

Boolean true

{n, FALSE, No, off}

Boolean false

Collection indicators

Key indicator

Value indicator

Nested series entry indicator

Separate in-line branch entries

[]

Surround in-line series branch

{}

Surround in-line keyed branch

Scalar indicators

Surround in-line unescaped scalar

Surround in-line escaped scalar

Block scalar indicator

Folded scalar indicator

Strip chomp modifier (|- or >-)

Keep chomp modifier (|+ or >+)

1-9

Explicit indentation modifier (|1 or >2).

Modifiers can be combined (|2-, >+1)

Special keys

Default "value" mapping key

Merge keys from another mapping

Misc indicators

Throwaway comment indicator

Both reserved for future use

Core types (default automatic tags)

!!map

{Hash table, dictionary, mapping}

!!seq

{List, array, tuple, vector, sequence}

!!str

Unicode string

Document indicators

Directive indicator

---

Document header

...

Document terminator

Alias indicators

Anchor property

Alias indicator

Code Difference Comparison

Online HTML Editor

Share Code Snippets

What is a YAML Cheat Sheet?

A YAML cheat sheet is a compact document that provides a quick and handy reference guide for the basics of YAML syntax and its conventions. This document is handy when working with YAML files, especially when you’re learning the language or need a refresher on its basic structure and syntax.

Some basic concepts:

Basics Rule
- Case sensitive.
- Indentation matters, no tabs, only spaces.
- Files end in '.yaml' or '.yml'.
Data Types
- Scalars: Basic data types like numbers, strings, booleans.
- Sequences: Arrays or Lists.
- Mappings: Hashes or Dictionaries.

YAML Tutorial | Learn YAML in 10 Minutes

Good specifications will always improve programmer productivity far better than any programming tool or technique.
Milt Bryce