PandasBasics.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Version 1.0.1"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Pandas basics "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Hi! In this programming assignment you need to refresh your `pandas` knowledge. You will need to do several [`groupby`](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.groupby.html)s and [`join`]()`s to solve the task. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import pandas as pd\n",
    "import numpy as np\n",
    "import os\n",
    "import matplotlib.pyplot as plt\n",
    "%matplotlib inline \n",
    "\n",
    "from grader import Grader"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 104,
   "metadata": {},
   "outputs": [],
   "source": [
    "DATA_FOLDER = '../readonly/final_project_data/'\n",
    "\n",
    "transactions    = pd.read_csv(os.path.join(DATA_FOLDER, 'sales_train.csv.gz'))\n",
    "items           = pd.read_csv(os.path.join(DATA_FOLDER, 'items.csv'))\n",
    "item_categories = pd.read_csv(os.path.join(DATA_FOLDER, 'item_categories.csv'))\n",
    "shops           = pd.read_csv(os.path.join(DATA_FOLDER, 'shops.csv'))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The dataset we are going to use is taken from the competition, that serves as the final project for this course. You can find complete data description at the [competition web page](https://www.kaggle.com/c/competitive-data-science-final-project/data). To join the competition use [this link](https://www.kaggle.com/t/1ea93815dca248e99221df42ebde3540)."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Grading"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We will create a grader instace below and use it to collect your answers. When function `submit_tag` is called, grader will store your answer *locally*. The answers will *not* be submited to the platform immediately so you can call `submit_tag` function as many times as you need. \n",
    "\n",
    "When you are ready to push your answers to the platform you should fill your credentials and run `submit` function in the <a href=\"#Authorization-&-Submission\">last paragraph</a>  of the assignment."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 105,
   "metadata": {},
   "outputs": [],
   "source": [
    "grader = Grader()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Task"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's start with a simple task. \n",
    "\n",
    "<ol start=\"0\">\n",
    "  <li><b>Print the shape of the loaded dataframes and use [`df.head`](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.head.html) function to print several rows. Examine the features you are given.</b></li>\n",
    "</ol>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 106,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "(2935849, 6)\n"
     ]
    },
    {
     "data": {
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       "<div>\n",
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       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>date</th>\n",
       "      <th>date_block_num</th>\n",
       "      <th>shop_id</th>\n",
       "      <th>item_id</th>\n",
       "      <th>item_price</th>\n",
       "      <th>item_cnt_day</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>02.01.2013</td>\n",
       "      <td>0</td>\n",
       "      <td>59</td>\n",
       "      <td>22154</td>\n",
       "      <td>999.00</td>\n",
       "      <td>1.0</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>03.01.2013</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2552</td>\n",
       "      <td>899.00</td>\n",
       "      <td>1.0</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>05.01.2013</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2552</td>\n",
       "      <td>899.00</td>\n",
       "      <td>-1.0</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>06.01.2013</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2554</td>\n",
       "      <td>1709.05</td>\n",
       "      <td>1.0</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>4</th>\n",
       "      <td>15.01.2013</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2555</td>\n",
       "      <td>1099.00</td>\n",
       "      <td>1.0</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "         date  date_block_num  shop_id  item_id  item_price  item_cnt_day\n",
       "0  02.01.2013               0       59    22154      999.00           1.0\n",
       "1  03.01.2013               0       25     2552      899.00           1.0\n",
       "2  05.01.2013               0       25     2552      899.00          -1.0\n",
       "3  06.01.2013               0       25     2554     1709.05           1.0\n",
       "4  15.01.2013               0       25     2555     1099.00           1.0"
      ]
     },
     "execution_count": 106,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "print(transactions.shape)\n",
    "transactions.head()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 107,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "(22170, 3)\n"
     ]
    },
    {
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       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>item_name</th>\n",
       "      <th>item_id</th>\n",
       "      <th>item_category_id</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>! ВО ВЛАСТИ НАВАЖДЕНИЯ (ПЛАСТ.)         D</td>\n",
       "      <td>0</td>\n",
       "      <td>40</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>!ABBYY FineReader 12 Professional Edition Full...</td>\n",
       "      <td>1</td>\n",
       "      <td>76</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>***В ЛУЧАХ СЛАВЫ   (UNV)                    D</td>\n",
       "      <td>2</td>\n",
       "      <td>40</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>***ГОЛУБАЯ ВОЛНА  (Univ)                      D</td>\n",
       "      <td>3</td>\n",
       "      <td>40</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>4</th>\n",
       "      <td>***КОРОБКА (СТЕКЛО)                       D</td>\n",
       "      <td>4</td>\n",
       "      <td>40</td>\n",
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       "  </tbody>\n",
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      "text/plain": [
       "                                           item_name  item_id  \\\n",
       "0          ! ВО ВЛАСТИ НАВАЖДЕНИЯ (ПЛАСТ.)         D        0   \n",
       "1  !ABBYY FineReader 12 Professional Edition Full...        1   \n",
       "2      ***В ЛУЧАХ СЛАВЫ   (UNV)                    D        2   \n",
       "3    ***ГОЛУБАЯ ВОЛНА  (Univ)                      D        3   \n",
       "4        ***КОРОБКА (СТЕКЛО)                       D        4   \n",
       "\n",
       "   item_category_id  \n",
       "0                40  \n",
       "1                76  \n",
       "2                40  \n",
       "3                40  \n",
       "4                40  "
      ]
     },
     "execution_count": 107,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "print(items.shape)\n",
    "items.head()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 108,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "(84, 2)\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style>\n",
       "    .dataframe thead tr:only-child th {\n",
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       "\n",
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       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>item_category_name</th>\n",
       "      <th>item_category_id</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>PC - Гарнитуры/Наушники</td>\n",
       "      <td>0</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>Аксессуары - PS2</td>\n",
       "      <td>1</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>Аксессуары - PS3</td>\n",
       "      <td>2</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>Аксессуары - PS4</td>\n",
       "      <td>3</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>4</th>\n",
       "      <td>Аксессуары - PSP</td>\n",
       "      <td>4</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "        item_category_name  item_category_id\n",
       "0  PC - Гарнитуры/Наушники                 0\n",
       "1         Аксессуары - PS2                 1\n",
       "2         Аксессуары - PS3                 2\n",
       "3         Аксессуары - PS4                 3\n",
       "4         Аксессуары - PSP                 4"
      ]
     },
     "execution_count": 108,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "print(item_categories.shape)\n",
    "item_categories.head()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 109,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "(60, 2)\n"
     ]
    },
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style>\n",
       "    .dataframe thead tr:only-child th {\n",
       "        text-align: right;\n",
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       "\n",
       "    .dataframe thead th {\n",
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       "    }\n",
       "\n",
       "    .dataframe tbody tr th {\n",
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       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>shop_name</th>\n",
       "      <th>shop_id</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>!Якутск Орджоникидзе, 56 фран</td>\n",
       "      <td>0</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>!Якутск ТЦ \"Центральный\" фран</td>\n",
       "      <td>1</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>Адыгея ТЦ \"Мега\"</td>\n",
       "      <td>2</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>Балашиха ТРК \"Октябрь-Киномир\"</td>\n",
       "      <td>3</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>4</th>\n",
       "      <td>Волжский ТЦ \"Волга Молл\"</td>\n",
       "      <td>4</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "                        shop_name  shop_id\n",
       "0   !Якутск Орджоникидзе, 56 фран        0\n",
       "1   !Якутск ТЦ \"Центральный\" фран        1\n",
       "2                Адыгея ТЦ \"Мега\"        2\n",
       "3  Балашиха ТРК \"Октябрь-Киномир\"        3\n",
       "4        Волжский ТЦ \"Волга Молл\"        4"
      ]
     },
     "execution_count": 109,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "print(shops.shape)\n",
    "shops.head()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now use your `pandas` skills to get answers for the following questions. \n",
    "The first question is:\n",
    "\n",
    "1. ** What was the maximum total revenue among all the shops in September, 2014?** \n",
    "\n",
    "\n",
    "* Hereinafter *revenue* refers to total sales minus value of goods returned.\n",
    "\n",
    "*Hints:*\n",
    "\n",
    "* Sometimes items are returned, find such examples in the dataset. \n",
    "* It is handy to split `date` field into [`day`, `month`, `year`] components and use `df.year == 14` and `df.month == 9` in order to select target subset of dates.\n",
    "* You may work with `date` feature as with srings, or you may first convert it to `pd.datetime` type with `pd.to_datetime` function, but do not forget to set correct `format` argument."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 110,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "CPU times: user 1min 25s, sys: 520 ms, total: 1min 25s\n",
      "Wall time: 1min 26s\n"
     ]
    }
   ],
   "source": [
    "%%time\n",
    "transactions.date = pd.to_datetime(transactions.date, format='%d.%m.%Y')\n",
    "transactions['year'] = [d.year for d in transactions.date]\n",
    "transactions['month'] = [d.month for d in transactions.date]\n",
    "transactions['dayofweek'] = [d.isoweekday() for d in transactions.date]\n",
    "transactions['day'] = [d.day for d in transactions.date]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 111,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
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       "        text-align: right;\n",
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       "\n",
       "    .dataframe thead th {\n",
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       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>date</th>\n",
       "      <th>date_block_num</th>\n",
       "      <th>shop_id</th>\n",
       "      <th>item_id</th>\n",
       "      <th>item_price</th>\n",
       "      <th>item_cnt_day</th>\n",
       "      <th>year</th>\n",
       "      <th>month</th>\n",
       "      <th>dayofweek</th>\n",
       "      <th>day</th>\n",
       "      <th>revenue</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>2013-01-02</td>\n",
       "      <td>0</td>\n",
       "      <td>59</td>\n",
       "      <td>22154</td>\n",
       "      <td>999.00</td>\n",
       "      <td>1.0</td>\n",
       "      <td>2013</td>\n",
       "      <td>1</td>\n",
       "      <td>3</td>\n",
       "      <td>2</td>\n",
       "      <td>999.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>2013-01-03</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2552</td>\n",
       "      <td>899.00</td>\n",
       "      <td>1.0</td>\n",
       "      <td>2013</td>\n",
       "      <td>1</td>\n",
       "      <td>4</td>\n",
       "      <td>3</td>\n",
       "      <td>899.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>2013-01-05</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2552</td>\n",
       "      <td>899.00</td>\n",
       "      <td>-1.0</td>\n",
       "      <td>2013</td>\n",
       "      <td>1</td>\n",
       "      <td>6</td>\n",
       "      <td>5</td>\n",
       "      <td>-899.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>2013-01-06</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2554</td>\n",
       "      <td>1709.05</td>\n",
       "      <td>1.0</td>\n",
       "      <td>2013</td>\n",
       "      <td>1</td>\n",
       "      <td>7</td>\n",
       "      <td>6</td>\n",
       "      <td>1709.05</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>4</th>\n",
       "      <td>2013-01-15</td>\n",
       "      <td>0</td>\n",
       "      <td>25</td>\n",
       "      <td>2555</td>\n",
       "      <td>1099.00</td>\n",
       "      <td>1.0</td>\n",
       "      <td>2013</td>\n",
       "      <td>1</td>\n",
       "      <td>2</td>\n",
       "      <td>15</td>\n",
       "      <td>1099.00</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "</div>"
      ],
      "text/plain": [
       "        date  date_block_num  shop_id  item_id  item_price  item_cnt_day  \\\n",
       "0 2013-01-02               0       59    22154      999.00           1.0   \n",
       "1 2013-01-03               0       25     2552      899.00           1.0   \n",
       "2 2013-01-05               0       25     2552      899.00          -1.0   \n",
       "3 2013-01-06               0       25     2554     1709.05           1.0   \n",
       "4 2013-01-15               0       25     2555     1099.00           1.0   \n",
       "\n",
       "   year  month  dayofweek  day  revenue  \n",
       "0  2013      1          3    2   999.00  \n",
       "1  2013      1          4    3   899.00  \n",
       "2  2013      1          6    5  -899.00  \n",
       "3  2013      1          7    6  1709.05  \n",
       "4  2013      1          2   15  1099.00  "
      ]
     },
     "execution_count": 111,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "transactions['revenue'] = transactions.item_cnt_day * transactions.item_price\n",
    "transactions.head()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 112,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "7982852.2\n",
      "Current answer for task max_revenue is: 7982852.2\n"
     ]
    }
   ],
   "source": [
    "max_revenue = transactions[(transactions['year'] == 2014) & (transactions['month'] == 9)].groupby(['shop_id'])['revenue'].sum().max()\n",
    "print(max_revenue)\n",
    "grader.submit_tag('max_revenue', max_revenue)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Great! Let's move on and answer another question:\n",
    "\n",
    "<ol start=\"2\">\n",
    "  <li><b>What item category generated the highest revenue in summer 2014?</b></li>\n",
    "</ol>\n",
    "\n",
    "* Submit `id` of the category found.\n",
    "    \n",
    "* Here we call \"summer\" the period from June to August.\n",
    "\n",
    "*Hints:*\n",
    "\n",
    "* Note, that for an object `x` of type `pd.Series`: `x.argmax()` returns **index** of the maximum element. `pd.Series` can have non-trivial index (not `[1, 2, 3, ... ]`)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 140,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<div>\n",
       "<style>\n",
       "    .dataframe thead tr:only-child th {\n",
       "        text-align: right;\n",
       "    }\n",
       "\n",
       "    .dataframe thead th {\n",
       "        text-align: left;\n",
       "    }\n",
       "\n",
       "    .dataframe tbody tr th {\n",
       "        vertical-align: top;\n",
       "    }\n",
       "</style>\n",
       "<table border=\"1\" class=\"dataframe\">\n",
       "  <thead>\n",
       "    <tr style=\"text-align: right;\">\n",
       "      <th></th>\n",
       "      <th>item_name</th>\n",
       "      <th>item_id</th>\n",
       "      <th>item_category_id</th>\n",
       "      <th>revenue</th>\n",
       "    </tr>\n",
       "  </thead>\n",
       "  <tbody>\n",
       "    <tr>\n",
       "      <th>0</th>\n",
       "      <td>! ВО ВЛАСТИ НАВАЖДЕНИЯ (ПЛАСТ.)         D</td>\n",
       "      <td>0</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>1</th>\n",
       "      <td>!ABBYY FineReader 12 Professional Edition Full...</td>\n",
       "      <td>1</td>\n",
       "      <td>76</td>\n",
       "      <td>8980.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>2</th>\n",
       "      <td>***В ЛУЧАХ СЛАВЫ   (UNV)                    D</td>\n",
       "      <td>2</td>\n",
       "      <td>40</td>\n",
       "      <td>58.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>3</th>\n",
       "      <td>***ГОЛУБАЯ ВОЛНА  (Univ)                      D</td>\n",
       "      <td>3</td>\n",
       "      <td>40</td>\n",
       "      <td>158.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>4</th>\n",
       "      <td>***КОРОБКА (СТЕКЛО)                       D</td>\n",
       "      <td>4</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>5</th>\n",
       "      <td>***НОВЫЕ АМЕРИКАНСКИЕ ГРАФФИТИ  (UNI)         ...</td>\n",
       "      <td>5</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>6</th>\n",
       "      <td>***УДАР ПО ВОРОТАМ (UNI)               D</td>\n",
       "      <td>6</td>\n",
       "      <td>40</td>\n",
       "      <td>100.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>7</th>\n",
       "      <td>***УДАР ПО ВОРОТАМ-2 (UNI)               D</td>\n",
       "      <td>7</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>8</th>\n",
       "      <td>***ЧАЙ С МУССОЛИНИ                     D</td>\n",
       "      <td>8</td>\n",
       "      <td>40</td>\n",
       "      <td>58.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>9</th>\n",
       "      <td>***ШУГАРЛЭНДСКИЙ ЭКСПРЕСС (UNI)             D</td>\n",
       "      <td>9</td>\n",
       "      <td>40</td>\n",
       "      <td>58.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>10</th>\n",
       "      <td>*ЗА ГРАНЬЮ СМЕРТИ                       D</td>\n",
       "      <td>10</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>11</th>\n",
       "      <td>*ЛИНИЯ СМЕРТИ                           D</td>\n",
       "      <td>11</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>12</th>\n",
       "      <td>*МИХЕЙ И ДЖУМАНДЖИ  Сука любовь</td>\n",
       "      <td>12</td>\n",
       "      <td>55</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>13</th>\n",
       "      <td>*СПАСАЯ ЭМИЛИ                           D</td>\n",
       "      <td>13</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>14</th>\n",
       "      <td>*ЧОКНУТЫЙ ПРОФЕССОР /МАГИЯ/             D</td>\n",
       "      <td>14</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>15</th>\n",
       "      <td>//АДРЕНАЛИН: ОДИН ПРОТИВ ВСЕХ (Регион)</td>\n",
       "      <td>15</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>16</th>\n",
       "      <td>//МОНГОЛ С.Бодров (Регион)</td>\n",
       "      <td>16</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>17</th>\n",
       "      <td>//НЕ ОСТАВЛЯЮЩИЙ СЛЕДА (Регион)</td>\n",
       "      <td>17</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>18</th>\n",
       "      <td>/БОМБА ДЛЯ НЕВЕСТЫ /2DVD/               D</td>\n",
       "      <td>18</td>\n",
       "      <td>40</td>\n",
       "      <td>58.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>19</th>\n",
       "      <td>/ЗОЛОТАЯ КОЛЛЕКЦИЯ м/ф-72</td>\n",
       "      <td>19</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>20</th>\n",
       "      <td>/ОДНАЖДЫ В КИТАЕ-2</td>\n",
       "      <td>20</td>\n",
       "      <td>40</td>\n",
       "      <td>58.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>21</th>\n",
       "      <td>/ПОСЛЕДНИЙ ШАНС</td>\n",
       "      <td>21</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22</th>\n",
       "      <td>/ПРОКЛЯТЬЕ ЭЛЬ ЧАРРО</td>\n",
       "      <td>22</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>23</th>\n",
       "      <td>/СЕВЕР И ЮГ /Ч.2/</td>\n",
       "      <td>23</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>24</th>\n",
       "      <td>/СМЕРТЕЛЬНЫЙ РАСКЛАД</td>\n",
       "      <td>24</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>25</th>\n",
       "      <td>/ТЫ  - ТРУП</td>\n",
       "      <td>25</td>\n",
       "      <td>40</td>\n",
       "      <td>58.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>26</th>\n",
       "      <td>/УМНОЖАЮЩИЙ ПЕЧАЛЬ т.2 (сер.3-4)</td>\n",
       "      <td>26</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>27</th>\n",
       "      <td>007 Legends [PS3, русская версия]</td>\n",
       "      <td>27</td>\n",
       "      <td>19</td>\n",
       "      <td>1494.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>28</th>\n",
       "      <td>007 Legends [PС, Jewel, русская версия]</td>\n",
       "      <td>28</td>\n",
       "      <td>30</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>29</th>\n",
       "      <td>007 Legends [Xbox 360, русская версия]</td>\n",
       "      <td>29</td>\n",
       "      <td>23</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>...</th>\n",
       "      <td>...</td>\n",
       "      <td>...</td>\n",
       "      <td>...</td>\n",
       "      <td>...</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22140</th>\n",
       "      <td>Я, РОБОТ (BD)</td>\n",
       "      <td>22140</td>\n",
       "      <td>37</td>\n",
       "      <td>7387.92</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22141</th>\n",
       "      <td>Я, СНОВА Я И МАМА</td>\n",
       "      <td>22141</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22142</th>\n",
       "      <td>Я, СНОВА Я И МАМА (BD)</td>\n",
       "      <td>22142</td>\n",
       "      <td>37</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22143</th>\n",
       "      <td>Я, ФРАНКЕНШТЕЙН</td>\n",
       "      <td>22143</td>\n",
       "      <td>40</td>\n",
       "      <td>27548.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22144</th>\n",
       "      <td>Я, ФРАНКЕНШТЕЙН (3D BD)</td>\n",
       "      <td>22144</td>\n",
       "      <td>38</td>\n",
       "      <td>23984.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22145</th>\n",
       "      <td>Я, ФРАНКЕНШТЕЙН (BD)</td>\n",
       "      <td>22145</td>\n",
       "      <td>37</td>\n",
       "      <td>10979.50</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22146</th>\n",
       "      <td>Я-ЛЕГЕНДА WB (BD)</td>\n",
       "      <td>22146</td>\n",
       "      <td>37</td>\n",
       "      <td>2993.50</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22147</th>\n",
       "      <td>Я-ЛЕГЕНДА WB (регион)</td>\n",
       "      <td>22147</td>\n",
       "      <td>40</td>\n",
       "      <td>58.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22148</th>\n",
       "      <td>Я-ЧЕТВЕРТЫЙ  WD</td>\n",
       "      <td>22148</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22149</th>\n",
       "      <td>Я-ЧЕТВЕРТЫЙ  WD (регион)</td>\n",
       "      <td>22149</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22150</th>\n",
       "      <td>Я-ЧЕТВЕРТЫЙ (BD)</td>\n",
       "      <td>22150</td>\n",
       "      <td>37</td>\n",
       "      <td>995.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22151</th>\n",
       "      <td>ЯВЛЕНИЕ (2012)</td>\n",
       "      <td>22151</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22152</th>\n",
       "      <td>ЯВЛЕНИЕ (2012) (регион)</td>\n",
       "      <td>22152</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22153</th>\n",
       "      <td>ЯВЛЕНИЕ (BD)</td>\n",
       "      <td>22153</td>\n",
       "      <td>37</td>\n",
       "      <td>457.63</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22154</th>\n",
       "      <td>ЯВЛЕНИЕ 2012 (BD)</td>\n",
       "      <td>22154</td>\n",
       "      <td>37</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22155</th>\n",
       "      <td>ЯДЫ, ИЛИ ВСЕМИРНАЯ ИСТОРИЯ ОТРАВЛЕНИЙ (BD)</td>\n",
       "      <td>22155</td>\n",
       "      <td>37</td>\n",
       "      <td>545.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22156</th>\n",
       "      <td>ЯДЫ, ИЛИ ВСЕМИРНАЯ ИСТОРИЯ ОТРАВЛЕНИЙ (регион)</td>\n",
       "      <td>22156</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22157</th>\n",
       "      <td>ЯЛТА 45</td>\n",
       "      <td>22157</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22158</th>\n",
       "      <td>ЯМА (rem)</td>\n",
       "      <td>22158</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22159</th>\n",
       "      <td>ЯНКОВСКИЙ</td>\n",
       "      <td>22159</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22160</th>\n",
       "      <td>ЯРМАРКА ТЩЕСЛАВИЯ (Регион)</td>\n",
       "      <td>22160</td>\n",
       "      <td>40</td>\n",
       "      <td>28.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22161</th>\n",
       "      <td>ЯРОСЛАВ. ТЫСЯЧУ ЛЕТ НАЗАД э (BD)</td>\n",
       "      <td>22161</td>\n",
       "      <td>37</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22162</th>\n",
       "      <td>ЯРОСТЬ</td>\n",
       "      <td>22162</td>\n",
       "      <td>40</td>\n",
       "      <td>28.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22163</th>\n",
       "      <td>ЯРОСТЬ ( регион)</td>\n",
       "      <td>22163</td>\n",
       "      <td>40</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22164</th>\n",
       "      <td>ЯРОСТЬ (BD)</td>\n",
       "      <td>22164</td>\n",
       "      <td>37</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22165</th>\n",
       "      <td>Ядерный титбит 2 [PC, Цифровая версия]</td>\n",
       "      <td>22165</td>\n",
       "      <td>31</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22166</th>\n",
       "      <td>Язык запросов 1С:Предприятия  [Цифровая версия]</td>\n",
       "      <td>22166</td>\n",
       "      <td>54</td>\n",
       "      <td>6000.00</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22167</th>\n",
       "      <td>Язык запросов 1С:Предприятия 8 (+CD). Хрустале...</td>\n",
       "      <td>22167</td>\n",
       "      <td>49</td>\n",
       "      <td>44730.40</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22168</th>\n",
       "      <td>Яйцо для Little Inu</td>\n",
       "      <td>22168</td>\n",
       "      <td>62</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "    <tr>\n",
       "      <th>22169</th>\n",
       "      <td>Яйцо дракона (Игра престолов)</td>\n",
       "      <td>22169</td>\n",
       "      <td>69</td>\n",
       "      <td>NaN</td>\n",
       "    </tr>\n",
       "  </tbody>\n",
       "</table>\n",
       "<p>22170 rows × 4 columns</p>\n",
       "</div>"
      ],
      "text/plain": [
       "                                               item_name  item_id  \\\n",
       "0              ! ВО ВЛАСТИ НАВАЖДЕНИЯ (ПЛАСТ.)         D        0   \n",
       "1      !ABBYY FineReader 12 Professional Edition Full...        1   \n",
       "2          ***В ЛУЧАХ СЛАВЫ   (UNV)                    D        2   \n",
       "3        ***ГОЛУБАЯ ВОЛНА  (Univ)                      D        3   \n",
       "4            ***КОРОБКА (СТЕКЛО)                       D        4   \n",
       "5      ***НОВЫЕ АМЕРИКАНСКИЕ ГРАФФИТИ  (UNI)         ...        5   \n",
       "6               ***УДАР ПО ВОРОТАМ (UNI)               D        6   \n",
       "7             ***УДАР ПО ВОРОТАМ-2 (UNI)               D        7   \n",
       "8               ***ЧАЙ С МУССОЛИНИ                     D        8   \n",
       "9          ***ШУГАРЛЭНДСКИЙ ЭКСПРЕСС (UNI)             D        9   \n",
       "10             *ЗА ГРАНЬЮ СМЕРТИ                       D       10   \n",
       "11             *ЛИНИЯ СМЕРТИ                           D       11   \n",
       "12                       *МИХЕЙ И ДЖУМАНДЖИ  Сука любовь       12   \n",
       "13             *СПАСАЯ ЭМИЛИ                           D       13   \n",
       "14             *ЧОКНУТЫЙ ПРОФЕССОР /МАГИЯ/             D       14   \n",
       "15                //АДРЕНАЛИН: ОДИН ПРОТИВ ВСЕХ (Регион)       15   \n",
       "16                            //МОНГОЛ С.Бодров (Регион)       16   \n",
       "17                       //НЕ ОСТАВЛЯЮЩИЙ СЛЕДА (Регион)       17   \n",
       "18             /БОМБА ДЛЯ НЕВЕСТЫ /2DVD/               D       18   \n",
       "19                             /ЗОЛОТАЯ КОЛЛЕКЦИЯ м/ф-72       19   \n",
       "20                                    /ОДНАЖДЫ В КИТАЕ-2       20   \n",
       "21                                       /ПОСЛЕДНИЙ ШАНС       21   \n",
       "22                                  /ПРОКЛЯТЬЕ ЭЛЬ ЧАРРО       22   \n",
       "23                                     /СЕВЕР И ЮГ /Ч.2/       23   \n",
       "24                                  /СМЕРТЕЛЬНЫЙ РАСКЛАД       24   \n",
       "25                                           /ТЫ  - ТРУП       25   \n",
       "26                      /УМНОЖАЮЩИЙ ПЕЧАЛЬ т.2 (сер.3-4)       26   \n",
       "27                     007 Legends [PS3, русская версия]       27   \n",
       "28               007 Legends [PС, Jewel, русская версия]       28   \n",
       "29                007 Legends [Xbox 360, русская версия]       29   \n",
       "...                                                  ...      ...   \n",
       "22140                                      Я, РОБОТ (BD)    22140   \n",
       "22141                                  Я, СНОВА Я И МАМА    22141   \n",
       "22142                             Я, СНОВА Я И МАМА (BD)    22142   \n",
       "22143                                    Я, ФРАНКЕНШТЕЙН    22143   \n",
       "22144                            Я, ФРАНКЕНШТЕЙН (3D BD)    22144   \n",
       "22145                               Я, ФРАНКЕНШТЕЙН (BD)    22145   \n",
       "22146                                  Я-ЛЕГЕНДА WB (BD)    22146   \n",
       "22147                              Я-ЛЕГЕНДА WB (регион)    22147   \n",
       "22148                                    Я-ЧЕТВЕРТЫЙ  WD    22148   \n",
       "22149                           Я-ЧЕТВЕРТЫЙ  WD (регион)    22149   \n",
       "22150                                   Я-ЧЕТВЕРТЫЙ (BD)    22150   \n",
       "22151                                     ЯВЛЕНИЕ (2012)    22151   \n",
       "22152                            ЯВЛЕНИЕ (2012) (регион)    22152   \n",
       "22153                                       ЯВЛЕНИЕ (BD)    22153   \n",
       "22154                                  ЯВЛЕНИЕ 2012 (BD)    22154   \n",
       "22155         ЯДЫ, ИЛИ ВСЕМИРНАЯ ИСТОРИЯ ОТРАВЛЕНИЙ (BD)    22155   \n",
       "22156     ЯДЫ, ИЛИ ВСЕМИРНАЯ ИСТОРИЯ ОТРАВЛЕНИЙ (регион)    22156   \n",
       "22157                                            ЯЛТА 45    22157   \n",
       "22158                                          ЯМА (rem)    22158   \n",
       "22159                                          ЯНКОВСКИЙ    22159   \n",
       "22160                         ЯРМАРКА ТЩЕСЛАВИЯ (Регион)    22160   \n",
       "22161                   ЯРОСЛАВ. ТЫСЯЧУ ЛЕТ НАЗАД э (BD)    22161   \n",
       "22162                                             ЯРОСТЬ    22162   \n",
       "22163                                   ЯРОСТЬ ( регион)    22163   \n",
       "22164                                        ЯРОСТЬ (BD)    22164   \n",
       "22165             Ядерный титбит 2 [PC, Цифровая версия]    22165   \n",
       "22166    Язык запросов 1С:Предприятия  [Цифровая версия]    22166   \n",
       "22167  Язык запросов 1С:Предприятия 8 (+CD). Хрустале...    22167   \n",
       "22168                                Яйцо для Little Inu    22168   \n",
       "22169                      Яйцо дракона (Игра престолов)    22169   \n",
       "\n",
       "       item_category_id   revenue  \n",
       "0                    40       NaN  \n",
       "1                    76   8980.00  \n",
       "2                    40     58.00  \n",
       "3                    40    158.00  \n",
       "4                    40       NaN  \n",
       "5                    40       NaN  \n",
       "6                    40    100.00  \n",
       "7                    40       NaN  \n",
       "8                    40     58.00  \n",
       "9                    40     58.00  \n",
       "10                   40       NaN  \n",
       "11                   40       NaN  \n",
       "12                   55       NaN  \n",
       "13                   40       NaN  \n",
       "14                   40       NaN  \n",
       "15                   40       NaN  \n",
       "16                   40       NaN  \n",
       "17                   40       NaN  \n",
       "18                   40     58.00  \n",
       "19                   40       NaN  \n",
       "20                   40     58.00  \n",
       "21                   40       NaN  \n",
       "22                   40       NaN  \n",
       "23                   40       NaN  \n",
       "24                   40       NaN  \n",
       "25                   40     58.00  \n",
       "26                   40       NaN  \n",
       "27                   19   1494.00  \n",
       "28                   30       NaN  \n",
       "29                   23       NaN  \n",
       "...                 ...       ...  \n",
       "22140                37   7387.92  \n",
       "22141                40       NaN  \n",
       "22142                37       NaN  \n",
       "22143                40  27548.00  \n",
       "22144                38  23984.00  \n",
       "22145                37  10979.50  \n",
       "22146                37   2993.50  \n",
       "22147                40     58.00  \n",
       "22148                40       NaN  \n",
       "22149                40       NaN  \n",
       "22150                37    995.00  \n",
       "22151                40       NaN  \n",
       "22152                40       NaN  \n",
       "22153                37    457.63  \n",
       "22154                37       NaN  \n",
       "22155                37    545.00  \n",
       "22156                40       NaN  \n",
       "22157                40       NaN  \n",
       "22158                40       NaN  \n",
       "22159                40       NaN  \n",
       "22160                40     28.00  \n",
       "22161                37       NaN  \n",
       "22162                40     28.00  \n",
       "22163                40       NaN  \n",
       "22164                37       NaN  \n",
       "22165                31       NaN  \n",
       "22166                54   6000.00  \n",
       "22167                49  44730.40  \n",
       "22168                62       NaN  \n",
       "22169                69       NaN  \n",
       "\n",
       "[22170 rows x 4 columns]"
      ]
     },
     "execution_count": 140,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "items"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 142,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Current answer for task category_id_with_max_revenue is: 20\n"
     ]
    }
   ],
   "source": [
    "items['revenue'] = transactions[(transactions['year'] == 2014) & (transactions['month'].\n",
    "                                                                              isin(np.arange(6, 9)))].groupby(['item_id'])['revenue'].sum()\n",
    "category_id_with_max_revenue = items.groupby(['item_category_id'])['revenue'].sum().argmax()\n",
    "grader.submit_tag('category_id_with_max_revenue', category_id_with_max_revenue)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<ol start=\"3\">\n",
    "  <li><b>How many items are there, such that their price stays constant (to the best of our knowledge) during the whole period of time?</b></li>\n",
    "</ol>\n",
    "\n",
    "* Let's assume, that the items are returned for the same price as they had been sold."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 137,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Current answer for task num_items_constant_price is: 5926\n"
     ]
    }
   ],
   "source": [
    "num_items_constant_price = sum([1 if item==1 else 0 for item in transactions.groupby(['item_id'])['item_price'].nunique()])\n",
    "grader.submit_tag('num_items_constant_price', num_items_constant_price)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Remember, the data can sometimes be noisy."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<ol start=\"4\">\n",
    "  <li><b>What was the variance of the number of sold items per day sequence for the shop with `shop_id = 25` in December, 2014?</b></li>\n",
    "</ol>\n",
    "\n",
    "* Fill `total_num_items_sold` and `days` arrays, and plot the sequence with the code below.\n",
    "* Then compute variance. Remember, there can be differences in how you normalize variance (biased or unbiased estimate, see [link](https://math.stackexchange.com/questions/496627/the-difference-between-unbiased-biased-estimator-variance)). Compute ***unbiased*** estimate (use the right value for `ddof` argument in `pd.var` or `np.var`)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 138,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "image/png": 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EzPWw5GGMMRFCVQ8oxe5PREhLjrc+D2OMMfvkFldQWllD/3pGWvmkJ7ejoKQqjFHVz5KH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\n/X8wkcNobLs6NQAAAABJRU5ErkJggg==\n",
      "text/plain": [
       "<matplotlib.figure.Figure at 0x7f5290a72d30>"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Current answer for task total_num_items_sold_var is: 117167.702299\n"
     ]
    }
   ],
   "source": [
    "shop_id = 25\n",
    "\n",
    "total_num_items_sold = transactions[(transactions.month==12) & (transactions.year==2014) & (transactions.shop_id==25)].groupby(['day'])['item_cnt_day'].sum()\n",
    "days = [day[0] for day in transactions[(transactions.month==12) & (transactions.year==2014) & (transactions.shop_id==25)].groupby(['day'])]\n",
    "\n",
    "# Plot it\n",
    "plt.plot(days, total_num_items_sold)\n",
    "plt.ylabel('Num items')\n",
    "plt.xlabel('Day')\n",
    "plt.title(\"Daily revenue for shop_id = 25\")\n",
    "plt.show()\n",
    "\n",
    "total_num_items_sold_var = np.var(total_num_items_sold, ddof=1)\n",
    "grader.submit_tag('total_num_items_sold_var', total_num_items_sold_var)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Authorization & Submission\n",
    "To submit assignment to Cousera platform, please, enter your e-mail and token into the variables below. You can generate token on the programming assignment page. *Note:* Token expires 30 minutes after generation."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 143,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "You want to submit these numbers:\n",
      "Task max_revenue: 7982852.2\n",
      "Task category_id_with_max_revenue: 20\n",
      "Task num_items_constant_price: 5926\n",
      "Task total_num_items_sold_var: 117167.702299\n"
     ]
    }
   ],
   "source": [
    "STUDENT_EMAIL = \n",
    "STUDENT_TOKEN = \n",
    "grader.status()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 94,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Submitted to Coursera platform. See results on assignment page!\n"
     ]
    }
   ],
   "source": [
    "grader.submit(STUDENT_EMAIL, STUDENT_TOKEN)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Well done! :)"
   ]
  }
 ],
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