YAML
YAML is a data serialisation language designed to be directly writable and readable by humans.
It’s a strict superset of JSON, with the addition of syntactically significant newlines and indentation, like Python. Unlike Python, however, YAML doesn’t allow literal tab characters for indentation.
--- # document start
# Comments in YAML look like this.
# YAML supports single-line comments.
################
# SCALAR TYPES #
################
# Our root object (which continues for the entire document) will be a map,
# which is equivalent to a dictionary, hash or object in other languages.
key: value
another_key: Another value goes here.
a_number_value: 100
scientific_notation: 1e+12
hex_notation: 0x123 # evaluates to 291
octal_notation: 0123 # evaluates to 83
# The number 1 will be interpreted as a number, not a boolean.
# If you want it to be interpreted as a boolean, use true.
boolean: true
null_value: null
another_null_value: ~
key with spaces: value
# Yes and No (doesn't matter the case) will be evaluated to boolean
# true and false values respectively.
# To use the actual value use single or double quotes.
no: no # evaluates to "no": false
yes: No # evaluates to "yes": false
not_enclosed: yes # evaluates to "not_enclosed": true
enclosed: "yes" # evaluates to "enclosed": yes
# Notice that strings don't need to be quoted. However, they can be.
however: 'A string, enclosed in quotes.'
'Keys can be quoted too.': "Useful if you want to put a ':' in your key."
single quotes: 'have ''one'' escape pattern'
double quotes: "have many: \", \0, \t, \u263A, \x0d\x0a == \r\n, and more."
# UTF-8/16/32 characters need to be encoded
Superscript two: \u00B2
# Special characters must be enclosed in single or double quotes
special_characters: "[ John ] & { Jane } - <Doe>"
# Multiple-line strings can be written either as a 'literal block' (using |),
# or a 'folded block' (using '>').
# Literal block turn every newline within the string into a literal newline (\n).
# Folded block removes newlines within the string.
literal_block: |
This entire block of text will be the value of the 'literal_block' key,
with line breaks being preserved.
The literal continues until de-dented, and the leading indentation is
stripped.
Any lines that are 'more-indented' keep the rest of their indentation -
these lines will be indented by 4 spaces.
folded_style: >
This entire block of text will be the value of 'folded_style', but this
time, all newlines will be replaced with a single space.
Blank lines, like above, are converted to a newline character.
'More-indented' lines keep their newlines, too -
this text will appear over two lines.
# |- and >- removes the trailing blank lines (also called literal/block "strip")
literal_strip: |-
This entire block of text will be the value of the 'literal_block' key,
with trailing blank line being stripped.
block_strip: >-
This entire block of text will be the value of 'folded_style', but this
time, all newlines will be replaced with a single space and
trailing blank line being stripped.
# |+ and >+ keeps trailing blank lines (also called literal/block "keep")
literal_keep: |+
This entire block of text will be the value of the 'literal_block' key,
with trailing blank line being kept.
block_keep: >+
This entire block of text will be the value of 'folded_style', but this
time, all newlines will be replaced with a single space and
trailing blank line being kept.
####################
# COLLECTION TYPES #
####################
# Nesting uses indentation. 2 space indent is preferred (but not required).
a_nested_map:
key: value
another_key: Another Value
another_nested_map:
hello: hello
# Maps don't have to have string keys.
0.25: a float key
# Keys can also be complex, like multi-line objects
# We use ? followed by a space to indicate the start of a complex key.
? |
This is a key
that has multiple lines
: and this is its value
# YAML also allows mapping between sequences with the complex key syntax
# Some language parsers might complain
# An example
? - Manchester United
- Real Madrid
: [ 2001-01-01, 2002-02-02 ]
# Sequences (equivalent to lists or arrays) look like this
# (note that the '-' counts as indentation):
a_sequence:
- Item 1
- Item 2
- 0.5 # sequences can contain disparate types.
- Item 4
- key: value
another_key: another_value
- - This is a sequence
- inside another sequence
- - - Nested sequence indicators
- can be collapsed
# Since YAML is a superset of JSON, you can also write JSON-style maps and
# sequences:
json_map: { "key": "value" }
json_seq: [ 3, 2, 1, "takeoff" ]
and quotes are optional: { key: [ 3, 2, 1, takeoff ] }
#######################
# EXTRA YAML FEATURES #
#######################
# YAML also has a handy feature called 'anchors', which let you easily duplicate
# content across your document.
# Anchors identified by & character which define the value.
# Aliases identified by * character which acts as "see above" command.
# Both of these keys will have the same value:
anchored_content: &anchor_name This string will appear as the value of two keys.
other_anchor: *anchor_name
# Anchors can be used to duplicate/inherit properties
base: &base
name: Everyone has same name
# The regexp << is called 'Merge Key Language-Independent Type'. It is used to
# indicate that all the keys of one or more specified maps should be inserted
# into the current map.
# NOTE: If key already exists alias will not be merged
foo:
<<: *base # doesn't merge the anchor
age: 10
name: John
bar:
<<: *base # base anchor will be merged
age: 20
# foo and bar would also have name: Everyone has same name
# YAML also has tags, which you can use to explicitly declare types.
# Syntax: !![typeName] [value]
explicit_boolean: !!bool true
explicit_integer: !!int 42
explicit_float: !!float -42.24
explicit_string: !!str 0.5
explicit_datetime: !!timestamp 2022-11-17 12:34:56.78 +9
explicit_null: !!null null
# Some parsers implement language specific tags, like this one for Python's
# complex number type.
python_complex_number: !!python/complex 1+2j
# We can also use yaml complex keys with language specific tags
? !!python/tuple [ 5, 7 ]
: Fifty Seven
# Would be {(5, 7): 'Fifty Seven'} in Python
####################
# EXTRA YAML TYPES #
####################
# Strings and numbers aren't the only scalars that YAML can understand.
# ISO-formatted date and datetime literals are also parsed.
datetime_canonical: 2001-12-15T02:59:43.1Z
datetime_space_separated_with_time_zone: 2001-12-14 21:59:43.10 -5
date_implicit: 2002-12-14
date_explicit: !!timestamp 2002-12-14
# The !!binary tag indicates that a string is actually a base64-encoded
# representation of a binary blob.
gif_file: !!binary |
R0lGODlhDAAMAIQAAP//9/X17unp5WZmZgAAAOfn515eXvPz7Y6OjuDg4J+fn5
OTk6enp56enmlpaWNjY6Ojo4SEhP/++f/++f/++f/++f/++f/++f/++f/++f/+
+f/++f/++f/++f/++f/++SH+Dk1hZGUgd2l0aCBHSU1QACwAAAAADAAMAAAFLC
AgjoEwnuNAFOhpEMTRiggcz4BNJHrv/zCFcLiwMWYNG84BwwEeECcgggoBADs=
# YAML also has a set type, which looks like this:
set:
? item1
? item2
? item3
or: { item1, item2, item3 }
# Sets are just maps with null values; the above is equivalent to:
set2:
item1: null
item2: null
item3: null
... # document endMore Resources
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