Question

How to parse/read a YAML file into a Python object?

For example, this YAML:

Person:
  name: XYZ

To this Python class:

class Person(yaml.YAMLObject):
  yaml_tag = 'Person'

  def __init__(self, name):
    self.name = name

I am using PyYAML by the way.

Answer 1

If your YAML file looks like this:

# tree format
treeroot:
    branch1:
        name: Node 1
        branch1-1:
            name: Node 1-1
    branch2:
        name: Node 2
        branch2-1:
            name: Node 2-1

And you’ve installed PyYAML like this:

pip install PyYAML

And the Python code looks like this:

import yaml
with open('tree.yaml') as f:
    # use safe_load instead load
    dataMap = yaml.safe_load(f)

The variable dataMap now contains a dictionary with the tree data. If you print dataMap using PrettyPrint, you will get something like:

{
    'treeroot': {
        'branch1': {
            'branch1-1': {
                'name': 'Node 1-1'
            },
            'name': 'Node 1'
        },
        'branch2': {
            'branch2-1': {
                'name': 'Node 2-1'
            },
            'name': 'Node 2'
        }
    }
}

So, now we have seen how to get data into our Python program. Saving data is just as easy:

with open('newtree.yaml', "w") as f:
    yaml.dump(dataMap, f)

You have a dictionary, and now you have to convert it to a Python object:

class Struct:
    def __init__(self, **entries): 
        self.__dict__.update(entries)

Then you can use:

>>> args = your YAML dictionary
>>> s = Struct(**args)
>>> s
<__main__.Struct instance at 0x01D6A738>
>>> s...

and follow "Convert Python dict to object".

For more information you can look at pyyaml.org and this.