add custom_filter union example

notebooks/08-custom-filters-infrastructure.ipynb

@@ -113,6 +113,42 @@
     "fig, ax = ox.plot.plot_graph(G, node_size=0, edge_color=\"w\", edge_linewidth=0.2)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Unions in custom filters\n",
+    "\n",
+    "You can pass a list via `custom_filter` to perform a union of multiple queries (i.e., an \"or\" operation)."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# add useful OSM tags to the default list, to retain them\n",
+    "ox.settings.useful_tags_way.extend([\"cycleway\", \"cycleway:left\", \"cycleway:right\"])\n",
+    "place = \"Bologna, Italia\"\n",
+    "\n",
+    "# get all ways with a 'cycleway:left'\n",
+    "cf1 = '[\"cycleway:left\"]'\n",
+    "G1 = ox.graph.graph_from_place(place, custom_filter=cf1, retain_all=True)\n",
+    "print(len(G1))\n",
+    "\n",
+    "# get all ways with a 'cycleway:right' tag\n",
+    "cf2 = '[\"cycleway:right\"]'\n",
+    "G2 = ox.graph.graph_from_place(place, custom_filter=cf2, retain_all=True)\n",
+    "print(len(G2))\n",
+    "\n",
+    "# union: get all ways with either a 'cycleway:right' or 'cycleway:left' tag\n",
+    "cf = [cf1, cf2]\n",
+    "ox.settings.useful_tags_way.extend([cf1, cf2])\n",
+    "G = ox.graph.graph_from_place(place, custom_filter=cf, retain_all=True)\n",
+    "print(len(G))"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,