fixes #162

fastcore/basics.py

@@ -611,10 +611,16 @@ def __getattr__(self,k):
         self.ready = False
         return self
 
+    def _call(self, *args, **kwargs):
+        self.args,self.kwargs,self.nms = [args],[kwargs],['__call__']
+        self.ready = True
+        return self
+
 # Cell
 class _SelfCls:
     def __getattr__(self,k): return getattr(_Self(),k)
     def __getitem__(self,i): return self.__getattr__('__getitem__')(i)
+    def __call__(self,*args,**kwargs): return self.__getattr__('_call')(*args,**kwargs)
 
 Self = _SelfCls()
 

nbs/01_basics.ipynb

@@ -3164,6 +3164,11 @@
     "            self.kwargs.append(None)\n",
     "        self.nms.append(k)\n",
     "        self.ready = False\n",
+    "        return self\n",
+    "    \n",
+    "    def _call(self, *args, **kwargs):\n",
+    "        self.args,self.kwargs,self.nms = [args],[kwargs],['__call__']\n",
+    "        self.ready = True\n",
     "        return self"
    ]
   },
@@ -3177,6 +3182,7 @@
     "class _SelfCls:\n",
     "    def __getattr__(self,k): return getattr(_Self(),k)\n",
     "    def __getitem__(self,i): return self.__getattr__('__getitem__')(i)\n",
+    "    def __call__(self,*args,**kwargs): return self.__getattr__('_call')(*args,**kwargs)\n",
     "\n",
     "Self = _SelfCls()"
    ]
@@ -3234,6 +3240,36 @@
     "test_eq(f(x), 1)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "`Self` is also callable, which creates a function which calls any function passed to it, using the arguments passed to `Self`:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[5, 2]"
+      ]
+     },
+     "execution_count": null,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "def f(a, b=3): return a+b+2\n",
+    "def g(a, b=3): return a*b\n",
+    "fg = Self(1,b=2)\n",
+    "list(map(fg, [f,g]))"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

nbs/03_xtras.ipynb

@@ -539,7 +539,7 @@
     {
      "data": {
       "text/plain": [
-       "['b', 'd', 'g', 'h', 'f', 'c', 'e', 'a']"
+       "['a', 'e', 'b', 'c', 'f', 'd', 'g', 'h']"
       ]
      },
      "execution_count": null,
@@ -869,7 +869,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "For example, we can use this to reimplement `imghdr.what` from the Python standard library, which is written in Python 3.7 as:"
+    "For example, we can use this to reimplement [`imghdr.what`](https://docs.python.org/3/library/imghdr.html#imghdr.what) from the Python standard library, which is [written in Python 3.9](https://github.com/python/cpython/blob/3.9/Lib/imghdr.py#L11) as:"
    ]
   },
   {
@@ -929,7 +929,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "With `maybe_open` and `first`, we can rewrite this in a much more concise and (in our opinion) clear way:"
+    "With `maybe_open`, `Self`, and `first`, we can rewrite this in a much more concise and (in our opinion) clear way:"
    ]
   },
   {
@@ -938,11 +938,10 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "def what(f):\n",
-    "    with maybe_open(f, 'rb') as f:\n",
-    "        location,h = f.tell(),f.read(32)\n",
-    "        f.seek(location)\n",
-    "        return first((tf(h,f) for tf in imghdr.tests), noop)"
+    "def what(file, h=None):\n",
+    "    if h is None:\n",
+    "        with maybe_open(file, 'rb') as f: h = f.peek(32)\n",
+    "    return first(map(Self(h,file), imghdr.tests), noop)"
    ]
   },
   {
@@ -972,6 +971,32 @@
     "what(fname)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "...along with the `h` parameter version:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "jpeg\n"
+     ]
+    }
+   ],
+   "source": [
+    "with open(fname,'rb') as f:\n",
+    "    h = f.read(32)\n",
+    "    print(what(None, h=h))"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,