Function-Decorators.ipynb

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    "def trace(fn):\n",
    "    def wrapped(x):\n",
    "        print('-> ', fn, '(', x, ')')\n",
    "        return fn(x)\n",
    "    return wrapped"
   ]
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   "source": [
    "@trace\n",
    "def triple(x):\n",
    "    return 3 * x"
   ]
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      "->  <function triple at 0x7f20eaf8b280> ( 12 )\n"
     ]
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       "36"
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   "source": [
    "triple(12)"
   ]
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   "source": [
    "In code, this decorator is equivalent to:"
   ]
  },
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   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "def triple(x):\n",
    "    return 3*x\n",
    "\n",
    "triple = trace(triple)"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The decorator symbol @ may also be followed by a call expression. The expression following @ is evaluated first (just as the name trace was evaluated above), the def statement second, and finally the result of evaluating the decorator expression is applied to the newly defined function, and the result is bound to the name in the def statement."
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