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Existing files
--------------
To directly render an existing DOT_ source file (e.g. created with other tools),
you can use the :func:`graphviz.render` function.
.. doctest::
>>> doctest_mark_exe() # skip this line
>>> import pathlib
>>> import graphviz
>>> src = 'digraph "the holy hand grenade" { rankdir=LR; 1 -> 2 -> 3 -> lob }'
>>> filepath = pathlib.Path('doctest-output/the-holy-hand-grenade.gv')
>>> filepath.write_text(src, encoding='ascii')
66
>>> graphviz.render('dot', 'png', filepath).replace('\\', '/')
'doctest-output/the-holy-hand-grenade.gv.png'
To directly display the rendered visualization of an existing DOT_ source file
inside a Jupyter `notebook <Jupyter notebook_>`_
or `Qt Console <Jupyter Qt Console_>`_,
you can use :meth:`graphviz.Source.from_file` (alternative constructor):
.. image:: _static/qtconsole-source.png
:align: center
Note that :meth:`~.Source.render` and :meth:`~.Source.view`
on :class:`.Source` instances returned by :meth:`graphviz.Source.from_file`
skip writing the loaded file back.
The same holds for :meth:`~.Source.save`.
The instances resolve default ``.save(skip_existing=None)``
to ``.save(skip_existing_run=True)``
to skip writing the read :attr:`~.Source.source` back into the same file
(specifically the same path that it was loaded from).
Call ``.save(skip_existing=False)`` if you want to re-write the loaded source.
.. admonition:: Historical note
Before version ``0.18`` of this library,
:meth:`.Source.save`, :meth:`.Source.render`, and :meth:`.Source.view`,
wrote the content read into source back into the file.
It was advised to use :func:`graphviz.render` and :func:`graphviz.view`
to directly work on files if the superfluous saving needed to be avoided.
.. include:: _links.rst
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