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|
.. _union_dict:
``UnionDict`` -- a dict with set like operations and keys as attributes
=======================================================================
This object combines the key-element storage of a ``dict`` with the union operation of a ``set()`` object. It is used in the ``cogent3.draw`` module, primarily for the ``figure`` and ``layout`` attributes.
Accessing elements of a ``UnionDict``
-------------------------------------
Keys in a ``UnionDict`` can be accessed like attributes
.. jupyter-execute::
from cogent3.util.union_dict import UnionDict
data = UnionDict(a=2, b={"c": 24, "d": [25]})
data.a
.. jupyter-execute::
data["a"]
.. jupyter-execute::
data.b.d
Updating a ``UnionDict``
------------------------
If you use the ``|`` bitwise operator to compare two dicts and the left one is a ``UnionDict``, a union operation is performed.
.. jupyter-execute::
from cogent3.util.union_dict import UnionDict
data = UnionDict(a=2, b={"c": 24, "d": [25]})
data.b |= {"d": 25}
data.b
This can also be done using the ``union`` method.
.. jupyter-execute::
data.b.union({"d": [25]})
.. jupyter-execute::
data.b
{"c": 24, "d": [25]}
Accessing a non-existent ``UnionDict`` key
------------------------------------------
.. jupyter-execute::
:raises: KeyError
from cogent3.util.union_dict import UnionDict
data = UnionDict(a=2, b={"c": 24, "d": [25]})
data["k"]
But if accessing as an attribute, you get an attribute error.
.. jupyter-execute::
:raises: AttributeError
data.k
|
