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

• https://github.com/yaml/pyyaml/issues/98

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)