20160930-dojo-dict-join.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Watch [Brandon Rhodes](http://pyvideo.org/speaker/brandon-rhodes.html)' \n",
    "[A Python Æsthetic: Beauty and Why I Python](http://pyvideo.org/pycon-ca-2012/a-python-sthetic-beauty-and-why-i-python.html)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Smith       CS101\n",
      "Johnson     EE201\n",
      "Williams    PH131\n",
      "Smith       PH132\n",
      "Jones       PH131\n",
      "Brown       EE201\n",
      "Williams    CS101\n"
     ]
    }
   ],
   "source": [
    "for line in open('semester.txt'):\n",
    "    print(line, end='')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Williams    Sophomore\n",
      "Johnson     Junior\n",
      "Smith       Freshman\n",
      "Jones       Sophomore\n",
      "Brown       Freshman\n"
     ]
    }
   ],
   "source": [
    "for line in open('students.txt'):\n",
    "    print(line, end='')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'Brown': 'EE201',\n",
       " 'Johnson': 'EE201',\n",
       " 'Jones': 'PH131',\n",
       " 'Smith': 'PH132',\n",
       " 'Williams': 'CS101'}"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "semester = dict(line.split() for line in open('semester.txt'))\n",
    "semester"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(('Smith', 'CS101'),\n",
       " ('Johnson', 'EE201'),\n",
       " ('Williams', 'PH131'),\n",
       " ('Smith', 'PH132'),\n",
       " ('Jones', 'PH131'),\n",
       " ('Brown', 'EE201'),\n",
       " ('Williams', 'CS101'))"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "semester = tuple(tuple(line.split()) for line in open('semester.txt'))\n",
    "semester"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "from collections import defaultdict, Counter"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defaultdict(list,\n",
       "            {'Brown': ['EE201'],\n",
       "             'Johnson': ['EE201'],\n",
       "             'Jones': ['PH131'],\n",
       "             'Smith': ['CS101', 'PH132'],\n",
       "             'Williams': ['PH131', 'CS101']})"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "courses_of_student = defaultdict(list)\n",
    "for line in open('semester.txt'):\n",
    "    name, course = line.split()\n",
    "    courses_of_student[name] += [course]\n",
    "courses_of_student"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'Brown': 'Freshman',\n",
       " 'Johnson': 'Junior',\n",
       " 'Jones': 'Sophomore',\n",
       " 'Smith': 'Freshman',\n",
       " 'Williams': 'Sophomore'}"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "year_of_student = dict(line.split() for line in open('students.txt'))\n",
    "year_of_student"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'Brown', 'Johnson', 'Jones', 'Smith', 'Williams'}"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "keys = courses_of_student.keys() & year_of_student.keys()\n",
    "keys"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defaultdict(collections.Counter,\n",
       "            {'Freshman': Counter({'CS101': 1, 'EE201': 1, 'PH132': 1}),\n",
       "             'Junior': Counter({'EE201': 1}),\n",
       "             'Sophomore': Counter({'CS101': 1, 'PH131': 2})})"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "courses_of_year = defaultdict(Counter)\n",
    "for student in courses_of_student.keys() & year_of_student.keys():\n",
    "    courses = courses_of_student[student]\n",
    "    year = year_of_student[student]\n",
    "    courses_of_year[year].update(courses)\n",
    "courses_of_year"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defaultdict(collections.Counter,\n",
       "            {'CS101': Counter({'Freshman': 1, 'Sophomore': 1}),\n",
       "             'EE201': Counter({'Freshman': 1, 'Junior': 1}),\n",
       "             'PH131': Counter({'Sophomore': 2}),\n",
       "             'PH132': Counter({'Freshman': 1})})"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "years_of_courses = defaultdict(Counter)\n",
    "for student in courses_of_student.keys() & year_of_student.keys():\n",
    "    courses = courses_of_student[student]\n",
    "    year = year_of_student[student]\n",
    "    for course in courses:\n",
    "        years_of_courses[course].update([year])\n",
    "years_of_courses"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The above was written before I saw how Brandon had written his code."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defaultdict(collections.Counter,\n",
       "            {'Freshman': Counter({'CS101': 1, 'EE201': 1, 'PH132': 1}),\n",
       "             'Junior': Counter({'EE201': 1}),\n",
       "             'Sophomore': Counter({'CS101': 1, 'PH131': 2})})"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "courses_of_year = defaultdict(Counter)\n",
    "for student in courses_of_student.keys() & year_of_student.keys():\n",
    "    courses = courses_of_student[student]\n",
    "    year = year_of_student[student]\n",
    "    for course in courses:\n",
    "        courses_of_year[year][course] +=1\n",
    "courses_of_year"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defaultdict(collections.Counter,\n",
       "            {'CS101': Counter({'Freshman': 1, 'Sophomore': 1}),\n",
       "             'EE201': Counter({'Freshman': 1, 'Junior': 1}),\n",
       "             'PH131': Counter({'Sophomore': 2}),\n",
       "             'PH132': Counter({'Freshman': 1})})"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "years_of_courses = defaultdict(Counter)\n",
    "for student in courses_of_student.keys() & year_of_student.keys():\n",
    "    courses = courses_of_student[student]\n",
    "    year = year_of_student[student]\n",
    "    for course in courses:\n",
    "        years_of_courses[course][year] += 1\n",
    "years_of_courses"
   ]
  }
 ],
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