my cheat sheet on PyYAML

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1 From pypi.org

"YAML is a data serialization format designed for human readability and interaction with scripting languages. PyYAML is a YAML parser and emitter for Python.

PyYAML features a complete YAML 1.1 parser, Unicode support, pickle support, capable extension API, and sensible error messages. PyYAML supports standard YAML tags and provides Python-specific tags that allow to represent an arbitrary Python object.

PyYAML is applicable for a broad range of tasks from complex configuration files to object serialization and persistence."

2 Installing

pip install yaml pyyaml

then in a python script: 

import yaml

3 PyYAML yaml.load(input) is deprecated

From PyYAML yaml.load deprecated in github for details but summarizing here, the new approach demands the loader be specified, as in:

  • yaml.load(input, Loader=BaseLoader ) or the equivalent:
  • yaml.base_load(input)
  1. Current loader choices (there are 4)
    1. BaseLoader: loads most basic YAML. All scalars are loaded as strings can also use yaml.base_load(input)
    2. SafeLoader: loads subset of YAML language, safely. Recommended for untrusted input can also use yaml.safe_load(input)
    3. FullLoader: the full YAML language. 5.3.1 still unsafe due to some CVEs can also use yaml.full_load(input)
    4. UnsafeLoader: also called Loader for backward compatibility can also use yaml.unsafe_load(input)
  2. Alternative syntaxes "sugar" methods:
    • yaml.safeload
    • yaml.fullload
    • yaml.unsafeload

    To silence warnings of unsafe load methods, yaml.warnings({'YAMLLoadWarning': False})

3.1 Writing a python dictionary to a YAML file with dump

The syntax is 

with open(r'E:\data\store_file.yaml', 'w') as file:
 documents = yaml.dump(dict_file, file)

You can also dump in a sorted keys order: 

with open(r'E:\data\store_file.yaml') as file:
 documents = yaml.load(file, Loader=yaml.FullLoader)

 sort_file = yaml.dump(doc, sort_keys=True)
 print(sort_file)

3.2 Summarizing: yaml.load and yaml.dump

If you data is safe and trusted, these two are all you need.

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