YAML

YAML is a popular format used in configurations. It is also the default format for Arjuna configuration and definition files.

Creating YAML Objects

Arjuna’s Json class provides with various helper methods to easily create a YAML object from various sources:

  • from_file: Load YAML from a file.

  • from_str: Load YAML from a string.

  • from_object: Load YAML from a Python built-in data type object.

The loaded object is returned as one of the following:

  • YamlDict

  • YamlList

  • If allow_any is set to True, then from_file, from_str and from_object calls return the same object as passed, if it is not a mapping or iterable.

YamlDict Object

YamlDict encapsulates the YAML dictionary and provides higher level methods for interaction.

It has the following properties:

  • raw_object: The underlying dictionary

  • size: Number of keys in the YamlDict

YamlList Object

YamlList encapsulates the YAML list and provides higher level methods for interaction.

It has the following properties:

  • raw_object: The underlying dictionary

  • size: Number of keys in the JsonList

== Operator with YamlDict and YamlList Objects

== operator is overridden for YamlDict and YamlList objects.

YamlDict supports comparison with a YamlDict or Python dict.

YamlList supports comparision with a YamlList or Python list.

yaml_dict_1 == yaml_dict_2
yaml_dict_1 == py_dict

yaml_list_1 == yaml_list_2
yaml_list_1 == py_list

Using !join construct

Arjuna provides !join construct to easily construct strings by concatenating the provided list. For example:

root: &BASE /path/to/root
patha: !join [*BASE, a]
pathb: !join [*BASE, b]

Once loaded this YAML is equivalent to the following Python dictionary:

{
    'root': '/path/to/root',
    'pathaa': '/path/to/roota',
    'pathb': '/path/to/rootb'
}