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Subgraphs & clusters
--------------------
:class:`.Graph` and :class:`.Digraph` objects have a
:meth:`~.Graph.subgraph` method for adding a subgraph to the instance.
There are two ways to use it: Either with a ready-made instance
of the same kind as the only argument (whose content is added as a subgraph)
or omitting the ``graph`` argument
(returning a context manager for defining the subgraph content more elegantly
within a ``with``-block).
First option, with ``graph`` as the only argument:
.. doctest::
>>> import graphviz # doctest: +NO_EXE
>>> p = graphviz.Graph(name='parent')
>>> p.edge('spam', 'eggs')
>>> c = graphviz.Graph(name='child', node_attr={'shape': 'box'})
>>> c.edge('foo', 'bar')
>>> p.subgraph(c)
Second usage, with a ``with``-block (omitting the ``graph`` argument):
.. doctest::
>>> p = graphviz.Graph('parent') # doctest: +NO_EXE
>>> p.edge('spam', 'eggs')
>>> with p.subgraph(name='child', node_attr={'shape': 'box'}) as c:
... c.edge('foo', 'bar')
Both produce the same result:
.. doctest::
>>> print(p.source) # doctest: +NORMALIZE_WHITESPACE +NO_EXE
graph parent {
spam -- eggs
subgraph child {
node [shape=box]
foo -- bar
}
}
.. tip::
If the ``name`` of a subgraph begins with ``'cluster'`` (all lowercase),
the layout engine treats it as a special **cluster** subgraph
(:ref:`example <cluster.py>` ).
See the `Subgraphs and Clusters` section in `DOT language <DOT_>`_.
When :meth:`~.Graph.subgraph` is used as a context manager,
the new graph instance is created with ``strict=None``
copying the **parent graph values** for ``directory``,
``engine``, ``format``, ``renderer``, ``formatter``,
and ``encoding``:
.. doctest::
>>> doctest_mark_exe() # skip this line
>>> p = graphviz.Graph('parent', directory='doctest-output')
>>> with p.subgraph(name='child') as c:
... c.edge('bacon', 'eggs')
... c.render().replace('\\', '/')
'doctest-output/child.gv.pdf'
.. note::
These copied attributes are only relevant for rendering the subgraph
**independently** (i.e. as a stand-alone graph) from within the ``with``-block.
.. include:: _links.rst
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