Add Logic to Your YAML Files
Load file.yaml
with YS:
!YS-v0:
# Get data from external sources:
names-url =:
"https://raw.githubusercontent.com/dominictarr/\
random-name/master/first-names.json"
name-list =: &first-names json/load(curl(names-url))
# Data object with literal keys and generated values:
name:: rand-nth(*first-names)
aka:: name-list.rand-nth()
age:: &num 2 * 3 * 7
color:: &hue qw(red green blue yellow)
.shuffle()
.first()
title:: "$(*num) shades of $(*hue)."
and get:
{
"name": "Dolores",
"aka": "Anita",
"age": 42,
"color": "green",
"title": "42 shades of green."
}
YS is a functional programming language with a clean YAML syntax.
YS can be used for enhancing ordinary YAML files with functional operations, such as:
- Import (parts of) other YAML files to any node
- String interpolation including function calls
- Data transforms including ones defined by you
This YS library should be a drop-in replacement for your current YAML loader!
Most existing YAML files are already valid YS files. This means that YS works as a normal YAML loader, but can also evaluate functional expressions if asked to.
Under the hood, YS code compiles to the Clojure programming language. This makes YS a complete functional programming language right out of the box.
Even though YS compiles to Clojure, and Clojure compiles to Java, there is no
dependency on Java or the JVM.
YS is compiled to a native shared library (libyamlscript.so
) that can be used
by any programming language that can load shared libraries.
To see the Clojure code that YS compiles to, you can use the YS
CLI binary ys
to run:
$ ys --compile file.ys
(let
[names-url "https://raw.githubusercontent.com/dominictarr/random-name/master/first-names.json"
name-list (_& 'first-names (json/load (curl names-url)))]
(%
"name" (rand-nth (_** 'first-names))
"aka" (rand-nth name-list)
"age" (_& 'num (mul+ 2 3 7))
"color" (_& 'hue (first (shuffle (qw red green blue yellow))))
"title" (str (_** 'num) " shades of " (_** 'hue) ".")))
File prog.py
:
from yamlscript import YAMLScript
ys = YAMLScript()
input = open('file.ys').read()
data = ys.load(input)
print(data)
File file.ys
:
!yamlscript/v0
name =: "World"
=>::
foo: [1, 2, ! inc(41)]
bar:: load("other.yaml")
baz:: "Hello, $name!"
File other.yaml
:
oh: Hello
Run:
$ python prog.py
{'foo': [1, 2, 42], 'bar': {'oh': 'Hello'}, 'baz': 'Hello, World!'}
You can install this module like any other Python module:
$ pip install yamlscript
but you will need to have a system install of libyamlscript.so
.
One simple way to do that is with:
$ curl https://yamlscript.org/install | bash
Note: The above command will install the latest version of the YAMLScript command line utility,
ys
, and the shared library,libyamlscript.so
, into~/local/bin
and~/.local/lib
respectively.
See https://github.com/yaml/yamlscript?#installing-yamlscript for more info.
Copyright 2022-2025 Ingy döt Net ingy@ingy.net
This project is licensed under the terms of the MIT
license.
See LICENSE for
more details.