docs/tutorials/hello_world.ipynb

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   "source": [
    "# Hello World"
   ]
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    "Let's start with a very simple example: a Bionic flow that generates the text\n",
    "\"Hello world!\"\n",
    "\n",
    "*(The code for this example is available in the Bionic repo at\n",
    "example/hello_world.py.)*\n",
    "\n",
    ".. literalinclude:: ../../example/hello_world.py\n",
    "    :language: python\n",
    "    :linenos:\n",
    "\n",
    "We can run this code (assuming we've checked out the ``bionic`` repo) like\n",
    "this:\n",
    "\n",
    ".. code-block:: bash\n",
    "\n",
    "    > cd bionic\n",
    "    > python example/hello_world.py\n",
    "    Hello world!\n",
    "\n",
    "We can also import it in an interpreter or notebook:"
   ]
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   "source": [
    "# Configure the PYTHONPATH for this notebook.\n",
    "import _tutorial_setup\n",
    "\n",
    "from example.hello_world import flow\n",
    "flow.get('message')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Although our `flow` object is immutable, we can easily make a new copy with a different value of `subject`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "new_flow = flow.setting('subject', 'universe')\n",
    "new_flow.get('message')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can also try changing the `message` directly:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "flow.setting('message', 'Goodbye world!').get('message')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
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    "As a convenience, `setting` and `get` can be called by an alternative syntax which makes it easier for your notebook or interpreter to autocomplete entity names:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "flow.setting.subject('universe').get.message()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Finally, we can visualize our flow as a directed acyclic graph:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "flow.render_dag()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "This flow doesn't do much, but it illustrates how flows can be constructed, used, and modified.\n",
    "The next tutorial will demonstrate a more practical example."
   ]
  }
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