item_22-Prefer	Helper Classes Over Bookkeeping with Dictionaries and Tuples.ipynb

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    "# 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": "code",
   "execution_count": 2,
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   "source": [
    "# Example 1\n",
    "class SimpleGradebook(object):\n",
    "    def __init__(self):\n",
    "        self._grades = {}\n",
    "\n",
    "    def add_student(self, name):\n",
    "        self._grades[name] = []\n",
    "\n",
    "    def report_grade(self, name, score):\n",
    "        self._grades[name].append(score)\n",
    "\n",
    "    def average_grade(self, name):\n",
    "        grades = self._grades[name]\n",
    "        return sum(grades) / len(grades)"
   ]
  },
  {
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   "execution_count": 3,
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     "text": [
      "90.0\n"
     ]
    }
   ],
   "source": [
    "# Example 2\n",
    "book = SimpleGradebook()\n",
    "book.add_student('Isaac Newton')\n",
    "book.report_grade('Isaac Newton', 90)\n",
    "book.report_grade('Isaac Newton', 95)\n",
    "book.report_grade('Isaac Newton', 85)\n",
    "print(book.average_grade('Isaac Newton'))"
   ]
  },
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   "source": [
    "# Example 3\n",
    "class BySubjectGradebook(object):\n",
    "    def __init__(self):\n",
    "        self._grades = {}\n",
    "\n",
    "    def add_student(self, name):\n",
    "        self._grades[name] = {}\n",
    "\n",
    "# Example 4\n",
    "    def report_grade(self, name, subject, grade):\n",
    "        by_subject = self._grades[name]\n",
    "        grade_list = by_subject.setdefault(subject, [])\n",
    "        grade_list.append(grade)\n",
    "\n",
    "    def average_grade(self, name):\n",
    "        by_subject = self._grades[name]\n",
    "        total, count = 0, 0\n",
    "        for grades in by_subject.values():\n",
    "            total += sum(grades)\n",
    "            count += len(grades)\n",
    "        return total / count"
   ]
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     "text": [
      "81.25\n"
     ]
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   "source": [
    "# Example 5\n",
    "book = BySubjectGradebook()\n",
    "book.add_student('Albert Einstein')\n",
    "book.report_grade('Albert Einstein', 'Math', 75)\n",
    "book.report_grade('Albert Einstein', 'Math', 65)\n",
    "book.report_grade('Albert Einstein', 'Gym', 90)\n",
    "book.report_grade('Albert Einstein', 'Gym', 95)\n",
    "print(book.average_grade('Albert Einstein'))"
   ]
  },
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   "source": [
    "# Example 6\n",
    "class WeightedGradebook(object):\n",
    "    def __init__(self):\n",
    "        self._grades = {}\n",
    "\n",
    "    def add_student(self, name):\n",
    "        self._grades[name] = {}\n",
    "\n",
    "    def report_grade(self, name, subject, score, weight):\n",
    "        by_subject = self._grades[name]\n",
    "        grade_list = by_subject.setdefault(subject, [])\n",
    "        grade_list.append((score, weight))\n",
    "\n",
    "# Example 7\n",
    "    def average_grade(self, name):\n",
    "        by_subject = self._grades[name]\n",
    "        score_sum, score_count = 0, 0\n",
    "        for subject, scores in by_subject.items():\n",
    "            subject_avg, total_weight = 0, 0\n",
    "            for score, weight in scores:\n",
    "                subject_avg += score * weight\n",
    "                total_weight += weight\n",
    "            score_sum += subject_avg / total_weight\n",
    "            score_count += 1\n",
    "        return score_sum / score_count"
   ]
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      "81.5\n"
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   "source": [
    "# Example 8\n",
    "book = WeightedGradebook()\n",
    "book.add_student('Albert Einstein')\n",
    "book.report_grade('Albert Einstein', 'Math', 80, 0.10)\n",
    "book.report_grade('Albert Einstein', 'Math', 80, 0.10)\n",
    "book.report_grade('Albert Einstein', 'Math', 70, 0.80)\n",
    "book.report_grade('Albert Einstein', 'Gym', 100, 0.40)\n",
    "book.report_grade('Albert Einstein', 'Gym', 85, 0.60)\n",
    "print(book.average_grade('Albert Einstein'))"
   ]
  },
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   "cell_type": "code",
   "execution_count": 8,
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     "text": [
      "89.5\n"
     ]
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   ],
   "source": [
    "# Example 9\n",
    "grades = []\n",
    "grades.append((95, 0.45))\n",
    "grades.append((85, 0.55))\n",
    "total = sum(score * weight for score, weight in grades)\n",
    "total_weight = sum(weight for _, weight in grades)\n",
    "average_grade = total / total_weight\n",
    "print(average_grade)"
   ]
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      "89.5\n"
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   "source": [
    "# Example 10\n",
    "grades = []\n",
    "grades.append((95, 0.45, 'Great job'))\n",
    "grades.append((85, 0.55, 'Better next time'))\n",
    "total = sum(score * weight for score, weight, _ in grades)\n",
    "total_weight = sum(weight for _, weight, _ in grades)\n",
    "average_grade = total / total_weight\n",
    "print(average_grade)"
   ]
  },
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   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
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   "outputs": [],
   "source": [
    "# Example 11\n",
    "import collections\n",
    "Grade = collections.namedtuple('Grade', ('score', 'weight'))"
   ]
  },
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   "execution_count": 11,
   "metadata": {
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   "source": [
    "# Example 12\n",
    "class Subject(object):\n",
    "    def __init__(self):\n",
    "        self._grades = []\n",
    "\n",
    "    def report_grade(self, score, weight):\n",
    "        self._grades.append(Grade(score, weight))\n",
    "\n",
    "    def average_grade(self):\n",
    "        total, total_weight = 0, 0\n",
    "        for grade in self._grades:\n",
    "            total += grade.score * grade.weight\n",
    "            total_weight += grade.weight\n",
    "        return total / total_weight"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
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   "source": [
    "# Example 13\n",
    "class Student(object):\n",
    "    def __init__(self):\n",
    "        self._subjects = {}\n",
    "\n",
    "    def subject(self, name):\n",
    "        if name not in self._subjects:\n",
    "            self._subjects[name] = Subject()\n",
    "        return self._subjects[name]\n",
    "\n",
    "    def average_grade(self):\n",
    "        total, count = 0, 0\n",
    "        for subject in self._subjects.values():\n",
    "            total += subject.average_grade()\n",
    "            count += 1\n",
    "        return total / count"
   ]
  },
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   "execution_count": 13,
   "metadata": {
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   "outputs": [],
   "source": [
    "# Example 14\n",
    "class Gradebook(object):\n",
    "    def __init__(self):\n",
    "        self._students = {}\n",
    "\n",
    "    def student(self, name):\n",
    "        if name not in self._students:\n",
    "            self._students[name] = Student()\n",
    "        return self._students[name]"
   ]
  },
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   "cell_type": "code",
   "execution_count": 14,
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     "text": [
      "81.5\n"
     ]
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   "source": [
    "# Example 15\n",
    "book = Gradebook()\n",
    "albert = book.student('Albert Einstein')\n",
    "math = albert.subject('Math')\n",
    "math.report_grade(80, 0.10)\n",
    "math.report_grade(80, 0.10)\n",
    "math.report_grade(70, 0.80)\n",
    "gym = albert.subject('Gym')\n",
    "gym.report_grade(100, 0.40)\n",
    "gym.report_grade(85, 0.60)\n",
    "print(albert.average_grade())"
   ]
  }
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