Demonstrate lazy tabs (#2479)

holoviz · Jul 2, 2021 · 9485449 · 9485449
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commit 9485449
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diff --git a/examples/reference/layouts/Tabs.ipynb b/examples/reference/layouts/Tabs.ipynb
@@ -140,6 +140,39 @@
     "tabs"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "If you want the `Tabs` to be completely lazy when rendering some output you can leverage a [ParamFunction or ParamMethod](../../user_guide/Param.ipynb) to ensure that the output is not computed until you navigate to the tab:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import time\n",
+    "import numpy as np\n",
+    "\n",
+    "def plot():\n",
+    "    time.sleep(1) # some long running calculation\n",
+    "    np.random.seed(tabs.active)\n",
+    "    xs, ys = np.random.randn(2, 100)\n",
+    "    p = figure(width=300, height=300, name=f'Scatter Seed {tabs.active}')\n",
+    "    p.scatter(xs, ys)\n",
+    "    return p\n",
+    "\n",
+    "p1 = pn.param.ParamFunction(plot, lazy=True, name='Seed 0')\n",
+    "p2 = pn.param.ParamFunction(plot, lazy=True, name='Seed 1')\n",
+    "p3 = pn.param.ParamFunction(plot, lazy=True, name='Seed 2')\n",
+    "\n",
+    "tabs = pn.Tabs(p1, p2, p3, dynamic=True)\n",
+    "\n",
+    "tabs"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

diff --git a/panel/param.py b/panel/param.py
@@ -825,8 +825,8 @@ class ParamFunction(ParamMethod):
     priority = 0.6
 
     def _link_object_params(self):
-        deps = self.object._dinfo
-        dep_params = list(deps['dependencies']) + list(deps.get('kw', {}).values())
+        deps = getattr(self.object, '_dinfo', {})
+        dep_params = list(deps.get('dependencies', [])) + list(deps.get('kw', {}).values())
         grouped = defaultdict(list)
         for dep in dep_params:
             grouped[id(dep.owner)].append(dep)
@@ -846,7 +846,11 @@ def _link_object_params(self):
 
     @classmethod
     def applies(cls, obj):
-        return isinstance(obj, types.FunctionType) and hasattr(obj, '_dinfo')
+        if isinstance(obj, types.FunctionType):
+            if hasattr(obj, '_dinfo'):
+                return True
+            return None
+        return False
 
 
 class JSONInit(param.Parameterized):