API

The API is mostly dynamic and so by nature difficult to document. If you have any suggestions for this please leave a note for me at www.bigjason.com.

Tree

You can call (almost) any method name on the Tree to create a new Node.

class datatree.Tree(*args, **kwargs)

Very top node in a datatree.

The Tree is the top node used to build a datatree.

COMMENT(text)

Adds a comment to the node. Alternatively you can use the // operator to create comments like this: tree // "A comment in here". With the XmlRenderer this would produce the comment <!--A comment in here -->.

Note: Comments are ignored by some of the renderers such as json and dict. Consult the documentation to find out the behaviour.

Parameters:text – Text of the comment.
DECLARE(name, *attrs)

Add an xml declaration to the datatree.

Note: This functionality is pretty limited for the time being, hopefully the API for this will become more clear with time.

Parameters:
  • name – Name of the declaration node.
  • attrs – Extra attributes to be added. Strings will be added as quoted strings. Symbols will be added as unquoted strings. Import the __ object and use it like this: __.SomeValue to add a symbol.
INSTRUCT(name='xml', **attrs)

Add an xml processing instruction.

Parameters:
  • name – Name of the instruction node. A value of xml will create the instruction <?xml ?>.
  • attrs – Any extra attributes for the instruction.
add_child_node(child_node)

For use when adding an existing Node.

register_renderer(klass)

Register a renderer class with the datatree rendering system.

Parameters:klass – Either a string with the fully qualified name of the renderer class to register, or the actual class itself. The name will be read from the class.
render(renderer='xml', as_root=False, **options)

Render the datatree using the provided renderer.

Parameters:
  • renderer – The name of the renderer to use. You may add more renderers by using the register_renderer method.
  • as_root – If True, the tree will be rendered from this node down, otherwise rendering will happen from the tree root.
  • options – Key value pairs of options that will be passed to the renderer.
to_string(level=0)

Create an ugly representation of the datatree from this node down. This is included as a debug aid and is not good for much else.

Node

Node is not instantiated directly, but is created for every node added to the Tree.

class datatree.tree.Node(node_name='root', node_value=None, **attrs)
COMMENT(text)

Adds a comment to the node. Alternatively you can use the // operator to create comments like this: tree // "A comment in here". With the XmlRenderer this would produce the comment <!--A comment in here -->.

Note: Comments are ignored by some of the renderers such as json and dict. Consult the documentation to find out the behaviour.

Parameters:text – Text of the comment.
add_child_node(child_node)

For use when adding an existing Node.

register_renderer(klass)

Register a renderer class with the datatree rendering system.

Parameters:klass – Either a string with the fully qualified name of the renderer class to register, or the actual class itself. The name will be read from the class.
render(renderer='xml', as_root=False, **options)

Render the datatree using the provided renderer.

Parameters:
  • renderer – The name of the renderer to use. You may add more renderers by using the register_renderer method.
  • as_root – If True, the tree will be rendered from this node down, otherwise rendering will happen from the tree root.
  • options – Key value pairs of options that will be passed to the renderer.
to_string(level=0)

Create an ugly representation of the datatree from this node down. This is included as a debug aid and is not good for much else.

Renderers

The renderers are responsible for converting the datatree into a usable format. Usually this format is a string, but sometimes other formats are used.

The examples in this section use this datatree:

from datatree import Tree

tree = Tree()
with tree.author() as author:
    author.name('Terry Pratchett')
    author.genre('Fantasy/Comedy')
    author // "Only 2 books listed"
    with author.novels(count=2) as novels:
        novels.novel('Small Gods', year=1992)
        novels.novel('The Fifth Elephant', year=1999)
        novels << Node("novel", "Guards! Guards!", year=1989)

XmlRenderer

Outputs the tree as an xml string. It is available under the alias 'xml'.

Options

Name Description Default
pretty When True, Outputs the xml document with pretty formatting. False
indent Used with pretty formatting. It is the string that will be used to indent each level. '    '

Example Output

tree('xml', pretty=True)

Or even shorter:

tree(pretty=True)

<author>
    <name>Terry Pratchett</name>
    <genre>Fantasy/Comedy</genre>
    <!-- Only 2 books listed -->
    <novels count="2">
        <novel year="1992">Small Gods</novel>
        <novel year="1999">The Fifth Elephant</novel>
        <novel year="1989">Guards! Guards!</novel>
    </novels>
</author>

JsonRenderer

Outputs the tree as json string using the python json module. It is available under the alias 'json', 'jsn' or 'js'.

Options

Name Description Default
pretty Outputs the json document with pretty formatting. False
sort_keys Sorts the keys in the json document. False

Example Output

tree('json', pretty=True)

{
    "author": {
        "genre": "Fantasy/Comedy", 
        "name": "Terry Pratchett", 
        "novels": [
            "Small Gods", 
            "The Fifth Elephant", 
            "Guards! Guards!"
        ]
    }
}

YamlRenderer

Outputs the tree as yaml string using the PyYAML package (which must be installed). It is available under the alias 'yaml' or 'yml'.

Options

Name Description Default
None    

Example Output

tree('yaml')

author:
  genre: Fantasy/Comedy
  name: Terry Pratchett
  novels: [Small Gods, The Fifth Elephant, Guards! Guards!]

DictRenderer

Outputs the tree as python dict. It is available under the alias 'dict' and 'dictionary'.

Options

Name Description Default
pretty_string When True, outputs the dict as a string with pretty formatting. False
allow_node_loss Determines if a duplicate node name will result in a node loss due to duplicate keys in the dict. False

Example Output

tree('dict', pretty_string=True)

{'author': {'genre': 'Fantasy/Comedy',
            'name': 'Terry Pratchett',
            'novels': ['Small Gods', 'The Fifth Elephant', 'Guards! Guards!']}}

Duplicate Node Names

While xml handles duplicate nodes just fine, python dicts and json for that matter do not allow duplicates. To handle this the DictRenderer will attempt to group nodes with the same name into a sub dictionary. This is why in the above example there is only one key for “novels”.

ETreeRenderer

Outputs the tree as an elementtree. It is available under the alias 'etree'.

Note: This module is not fully implemented. It supports the basic node types, but not comments, declarations, instructions or cdata.

Options

Name Description Default
as_string Outputs the document as a string instead of a populated elementtree. False

Implementing a Renderer

You can implement your own renderer. Just look at the source for one of the existing renderers and implement the same methods, and then register your plugin with the register_renderer() method.