fixes #196

Author: jph00

fastcore/_nbdev.py

@@ -100,6 +100,7 @@
          "instantiate": "01_basics.ipynb",
          "using_attr": "01_basics.ipynb",
          "Self": "01_basics.ipynb",
+         "Stateful": "01_basics.ipynb",
          "PrettyString": "01_basics.ipynb",
          "even_mults": "01_basics.ipynb",
          "num_cpus": "01_basics.ipynb",

fastcore/basics.py

@@ -10,7 +10,8 @@
            'filter_values', 'cycle', 'zip_cycle', 'sorted_ex', 'negate_func', 'argwhere', 'filter_ex', 'range_of',
            'renumerate', 'first', 'nested_attr', 'nested_idx', 'num_methods', 'rnum_methods', 'inum_methods',
            'fastuple', 'arg0', 'arg1', 'arg2', 'arg3', 'arg4', 'bind', 'map_ex', 'compose', 'maps', 'partialler',
-           'instantiate', 'using_attr', 'Self', 'Self', 'PrettyString', 'even_mults', 'num_cpus', 'add_props', 'typed']
+           'instantiate', 'using_attr', 'Self', 'Self', 'Stateful', 'PrettyString', 'even_mults', 'num_cpus',
+           'add_props', 'typed']
 
 # Cell
 from .imports import *
@@ -660,6 +661,26 @@ def __call__(self,*args,**kwargs): return self.__getattr__('_call')(*args,**kwar
 # Cell
 #nbdev_comment _all_ = ['Self']
 
+# Cell
+class Stateful:
+    "A base class/mixin for objects that should not serialize all their state"
+    _stateattrs=()
+    def __init__(self,*args,**kwargs):
+        self._init_state()
+        super().__init__(*args,**kwargs)
+
+    def __getstate__(self):
+        return {k:v for k,v in self.__dict__.items()
+                if k not in self._stateattrs+('_state',)}
+
+    def __setstate__(self, state):
+        self.__dict__.update(state)
+        self._init_state()
+
+    def _init_state(self):
+        "Override for custom deserialization logic"
+        self._state = {}
+
 # Cell
 class PrettyString(str):
     "Little hack to get strings to show properly in Jupyter."

nbs/01_basics.ipynb

@@ -3531,6 +3531,79 @@
     "## Other Helpers"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "#export\n",
+    "class Stateful:\n",
+    "    \"A base class/mixin for objects that should not serialize all their state\"\n",
+    "    _stateattrs=()\n",
+    "    def __init__(self,*args,**kwargs):\n",
+    "        self._init_state()\n",
+    "        super().__init__(*args,**kwargs)\n",
+    "    \n",
+    "    def __getstate__(self):\n",
+    "        return {k:v for k,v in self.__dict__.items()\n",
+    "                if k not in self._stateattrs+('_state',)}\n",
+    "    \n",
+    "    def __setstate__(self, state):\n",
+    "        self.__dict__.update(state)\n",
+    "        self._init_state()\n",
+    "\n",
+    "    def _init_state(self):\n",
+    "        \"Override for custom deserialization logic\"\n",
+    "        self._state = {}"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/markdown": [
+       "<h4 id=\"Stateful\" class=\"doc_header\"><code>class</code> <code>Stateful</code><a href=\"\" class=\"source_link\" style=\"float:right\">[source]</a></h4>\n",
+       "\n",
+       "> <code>Stateful</code>(**\\*`args`**, **\\*\\*`kwargs`**)\n",
+       "\n",
+       "A base class/mixin for objects that should not serialize all their state"
+      ],
+      "text/plain": [
+       "<IPython.core.display.Markdown object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "show_doc(Stateful, title_level=4)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "class _T(Stateful):\n",
+    "    def __init__(self):\n",
+    "        super().__init__()\n",
+    "        self.a=1\n",
+    "        self._state['test']=2\n",
+    "\n",
+    "t = _T()\n",
+    "t2 = pickle.loads(pickle.dumps(t))\n",
+    "test_eq(t.a,1)\n",
+    "test_eq(t._state['test'],2)\n",
+    "test_eq(t2.a,1)\n",
+    "test_eq(t2._state,{})"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,