Tree-like dictionaries are gross and hard to work with. Use elementtree for nested data.
In Python, most people’s instinct is to model tree-like structures with nested dictionaries. An organization chart from a nuclear power plant is a simple example:
The old me would have rushed to model this like so:
org = {'name':'Monty',
'title':'CEO',
'boss_of':[
{'name':'Waylon',
'title':'Flunkie',
'boss_of':[
{'name':'Carl',
'title':'Engineer',
'boss_of': None},
{'name':'Lenny',
'title':'Engineer',
'boss_of': None},
{'name':'Homer',
'title':'Safety Iinspector',
'boss_of': None}
]
}]
}
This is annoying to type and even harder to read. Keeping track of quotes, brackets and commas is frustrating. Imagine the pain when of a larger or more complex tree.
Fear not. elementtree makes things super-easy when dealing with nested data.
“But wait”, you say. “You’re not doing XML!”
Say it with me: elementtree is not XML. Yes, it’s good at serializing to and de-serializing from XML, but it’s very useful even if you never read or generate a lick of markup.
Here’s the same org chart using Element. Much shorter, less error-prone, and easier on the eyeballs:
from elementtree.ElementTree import Element
from elementtree.ElementTree import SubElement
burns = Element('emp', name="Monty", title="CEO")
smithers = SubElement(burns, 'emp', name="Waylan", title="Flunkie")
karl = SubElement(smithers, 'emp', name="Carl", title="Engineer")
lenny = SubElement(smithers, 'emp', name="Lenny", title="Engineer")
homer = SubElement(smithers, 'emp', name="Homer", title="Inspector")
I didn’t create a whole class to help me model the nested data; that would have been overkill. I just used Elements to string together related data. Now it’s easy to navigate the tree in idiot-proof fashion with methods like getchildren and getiterator.
Nested data pops up quite often, and it’s nice to have a good tool for dealing with it gracefully.
