item_25-Initialize Parent Classes with super.ipynb

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    "# %load ../example_code/item_25.py\n",
    "#!/usr/bin/env python3\n",
    "\n",
    "# Copyright 2014 Brett Slatkin, Pearson Education Inc.\n",
    "#\n",
    "# Licensed under the Apache License, Version 2.0 (the \"License\");\n",
    "# you may not use this file except in compliance with the License.\n",
    "# You may obtain a copy of the License at\n",
    "#\n",
    "#     http://www.apache.org/licenses/LICENSE-2.0\n",
    "#\n",
    "# Unless required by applicable law or agreed to in writing, software\n",
    "# distributed under the License is distributed on an \"AS IS\" BASIS,\n",
    "# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n",
    "# See the License for the specific language governing permissions and\n",
    "# limitations under the License.\n",
    "\n",
    "# Preamble to mimick book environment\n",
    "import logging\n",
    "from pprint import pprint\n",
    "from sys import stdout as STDOUT"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## use\tthe\tsuper\tbuilt-in\tfunction\tto\tinitialize\tparent\tclasses."
   ]
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     "text": [
      "10\n"
     ]
    }
   ],
   "source": [
    "# Example 1\n",
    "class MyBaseClass(object):\n",
    "    def __init__(self, value):\n",
    "        self.value = value\n",
    "\n",
    "class MyChildClass(MyBaseClass):\n",
    "    def __init__(self):\n",
    "        MyBaseClass.__init__(self, 5)\n",
    "\n",
    "    def times_two(self):\n",
    "        return self.value * 2\n",
    "\n",
    "foo = MyChildClass()\n",
    "print(foo.times_two())"
   ]
  },
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   "source": [
    "# Example 2\n",
    "class TimesTwo(object):\n",
    "    def __init__(self):\n",
    "        self.value *= 2\n",
    "\n",
    "class PlusFive(object):\n",
    "    def __init__(self):\n",
    "        self.value += 5"
   ]
  },
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   "source": [
    "# Example 3\n",
    "class OneWay(MyBaseClass, TimesTwo, PlusFive):\n",
    "    def __init__(self, value):\n",
    "        MyBaseClass.__init__(self, value)\n",
    "        TimesTwo.__init__(self)\n",
    "        PlusFive.__init__(self)"
   ]
  },
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   "execution_count": 5,
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   "outputs": [
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     "text": [
      "First ordering is (5 * 2) + 5 = 15\n"
     ]
    }
   ],
   "source": [
    "# Example 4\n",
    "foo = OneWay(5)\n",
    "print('First ordering is (5 * 2) + 5 =', foo.value)"
   ]
  },
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   "execution_count": 6,
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   "source": [
    "# Example 5\n",
    "class AnotherWay(MyBaseClass, PlusFive, TimesTwo):\n",
    "    def __init__(self, value):\n",
    "        MyBaseClass.__init__(self, value)\n",
    "        TimesTwo.__init__(self)\n",
    "        PlusFive.__init__(self)"
   ]
  },
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   "execution_count": 7,
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   "outputs": [
    {
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     "text": [
      "Second ordering still is 15\n"
     ]
    }
   ],
   "source": [
    "# Example 6\n",
    "bar = AnotherWay(5)\n",
    "print('Second ordering still is', bar.value)"
   ]
  },
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   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
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   "outputs": [],
   "source": [
    "# Example 7\n",
    "class TimesFive(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        MyBaseClass.__init__(self, value)\n",
    "        self.value *= 5\n",
    "\n",
    "class PlusTwo(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        MyBaseClass.__init__(self, value)\n",
    "        self.value += 2"
   ]
  },
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   "execution_count": 9,
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   "outputs": [
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     "name": "stdout",
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     "text": [
      "Should be (5 * 5) + 2 = 27 but is 7\n"
     ]
    }
   ],
   "source": [
    "# Example 8\n",
    "class ThisWay(TimesFive, PlusTwo):\n",
    "    def __init__(self, value):\n",
    "        TimesFive.__init__(self, value)\n",
    "        PlusTwo.__init__(self, value)\n",
    "\n",
    "foo = ThisWay(5)\n",
    "print('Should be (5 * 5) + 2 = 27 but is', foo.value)"
   ]
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   "source": [
    "# Example 9\n",
    "class MyBaseClass(object):\n",
    "    def __init__(self, value):\n",
    "        self.value = value\n",
    "\n",
    "class TimesFiveCorrect(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super(TimesFiveCorrect, self).__init__(value)\n",
    "        self.value *= 5\n",
    "\n",
    "class PlusTwoCorrect(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super(PlusTwoCorrect, self).__init__(value)\n",
    "        self.value += 2\n"
   ]
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   "execution_count": 11,
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Should be 5 * (5 + 2) = 35 and is 35\n"
     ]
    }
   ],
   "source": [
    "# Example 10\n",
    "class MyBaseClass(object):\n",
    "    def __init__(self, value):\n",
    "        self.value = value\n",
    "\n",
    "class TimesFiveCorrect(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super(TimesFiveCorrect, self).__init__(value)\n",
    "        self.value *= 5\n",
    "\n",
    "class PlusTwoCorrect(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super(PlusTwoCorrect, self).__init__(value)\n",
    "        self.value += 2\n",
    "\n",
    "class GoodWay(TimesFiveCorrect, PlusTwoCorrect):\n",
    "    def __init__(self, value):\n",
    "        super(GoodWay, self).__init__(value)\n",
    "\n",
    "foo = GoodWay(5)\n",
    "print('Should be 5 * (5 + 2) = 35 and is', foo.value)\n"
   ]
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   "execution_count": 12,
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     "text": [
      "[<class '__main__.GoodWay'>,\n",
      " <class '__main__.TimesFiveCorrect'>,\n",
      " <class '__main__.PlusTwoCorrect'>,\n",
      " <class '__main__.MyBaseClass'>,\n",
      " <class 'object'>]\n",
      "[<class '__main__.GoodWay'>,\n",
      " <class '__main__.TimesFiveCorrect'>,\n",
      " <class '__main__.PlusTwoCorrect'>,\n",
      " <class '__main__.MyBaseClass'>,\n",
      " <class 'object'>]\n"
     ]
    }
   ],
   "source": [
    "# Example 11\n",
    "# This is pretending to be Python 2 but it's not\n",
    "class MyBaseClass(object):\n",
    "    def __init__(self, value):\n",
    "        self.value = value\n",
    "\n",
    "class TimesFiveCorrect(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super(TimesFiveCorrect, self).__init__(value)\n",
    "        self.value *= 5\n",
    "\n",
    "class PlusTwoCorrect(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super(PlusTwoCorrect, self).__init__(value)\n",
    "        self.value += 2\n",
    "\n",
    "class GoodWay(TimesFiveCorrect, PlusTwoCorrect):\n",
    "    def __init__(self, value):\n",
    "        super(GoodWay, self).__init__(value)\n",
    "\n",
    "before_pprint = pprint\n",
    "pprint(GoodWay.mro())\n",
    "from pprint import pprint\n",
    "pprint(GoodWay.mro())\n",
    "pprint = pprint"
   ]
  },
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   "execution_count": 13,
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   "source": [
    "# Example 12\n",
    "class Explicit(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super(__class__, self).__init__(value * 2)\n",
    "\n",
    "class Implicit(MyBaseClass):\n",
    "    def __init__(self, value):\n",
    "        super().__init__(value * 2)\n",
    "\n",
    "assert Explicit(10).value == Implicit(10).value"
   ]
  }
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