YAML Multi-Line Arrays

In YAML, you can easily create multi-line strings. However, I would like the ability to create a multi-line array (mainly for readibility within config files) using the | character.

A YAML array can be represented as: ['key1', 'key2', 'key3'].

A YAML sequence uses a dash followed by a space and then a string:

- String1 - String2 - String3 

This would evaluate to: ['string1', 'string2', 'string3'].

A YAML mapping is an array of key and value pairs that we see all the time in YAML:

Key1: string1 Key2: string2 Key3: string3 

This is all well and good, but I can't for the life of me see how to do a multi-line array. Something like this:

| ['string1', 'string2', 'string3'] ['string4', 'string5', 'string6'] 

Short of creating multiple array mappings in YAML and merging them in my programming language of choice, is there any way to achieve multi-line arrays, maybe with { } like Python has but in YAML?

5 Answers

A YAML sequence is an array. So this is the right way to express it:

key: - string1 - string2 - string3 - string4 - string5 - string6 

That's identical in meaning to:

key: ['string1', 'string2', 'string3', 'string4', 'string5', 'string6'] 

It's also legal to split a single-line array over several lines:

key: ['string1', 'string2', 'string3', 'string4', 'string5', 'string6'] 

and even have multi-line strings in single-line arrays:

key: ['string1', 'long string', 'string3', 'string4', 'string5', 'string6'] 

have you tried this?

- name: Jack age: 32 - name: Claudia age: 25 

I get this: [{"name"=>"Jack", "age"=>32}, {"name"=>"Claudia", "age"=>25}] (I use the YAML Ruby class).

If what you are needing is an array of arrays, you can do this way:

key: - [ 'value11', 'value12', 'value13' ] - [ 'value21', 'value22', 'value23' ] 

The following would work:

myarray: [ String1, String2, String3, String4, String5, String5, String7 ] 

I tested it using the snakeyaml implementation, I am not sure about other implementations though.

The following works for me and its good from readability point of view when the number of array element values is small:

key: [string1, string2, string3, string4, string5, string6] 

This has been tested to work with snakeyaml and ruamel.yaml.