YAML in Python

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PyYAML

https://pyyaml.org/

https://pyyaml.org/wiki/PyYAMLDocumentation

https://pypi.org/project/PyYAML/

PyYAML provides YAML serialization/deserialization in Python.

Installation

pip install pyyaml

requirements.txt:

pyyaml == 5.3.1

To install, see the "Installation" section from https://pyyaml.org/wiki/PyYAMLDocumentation.

Deserialize YAML

import yaml

with open('some-file.yaml', 'rt') as f:
  content = f.read()
data = yaml.load(content, Loader=yaml.Loader)

Serialize YAML

import yaml

# with the default flow style, the document is rendered in a non-indented manner 
print (yaml.dump(data, default_flow_style=False))

Safely Navigate a Complex Data Structure

Suggestions on how to safely recursively navigate a complex data structure:

Safely Navigate a Complex Data Structure

Representers

Configure yaml.dump() to render blank instead of null

PyYAML dump() uses Representer() to represent None. By default, the representer dump() is configured with represents None as "null". To change that:

1. Define a method that "represents" None

def representer_for_none(self, _):
    return self.represent_scalar('tag:yaml.org,2002:null', '')

2. Add it to the module:

import yaml

[...]

yaml.add_representer(type(None), represent_none)

This will render:

d = {
    'a': None,
    'b': 'c'
}

as:

a:
b: c

what is the lifecycle of the method registered to the module?

Configure yaml.dump() to render | multi-lines

def literal_presenter(dumper, data):
    return dumper.represent_scalar('tag:yaml.org,2002:str', data, style='|')

def default_presenter(dumper, data):
     return dumper.represent_scalar('tag:yaml.org,2002:str', data, style='')

try:
   yaml.add_representer(str, literal_presenter)
   yaml_text = yaml.dump(config)
   return yaml_text
finally:
    yaml.add_representer(str, default_presenter)