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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Warmup 1: Take a look at some list methods\n",
+    "\n",
+    "List methods [here](https://www.w3schools.com/python/python_ref_list.asp)..."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "dairy = [\"milk\", \"ice cream\", \"cheese\", \"yogurt\", \"butter\"]\n",
+    "\n",
+    "# use the .index() method to get the index of \"ice cream\"\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Warmup 2: Because a list is a sequence, we can use the `in` operator"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "food_shelf = [\"peanut butter\", \"milk\", \"bread\", \"cheese\", \"YOGURT\"]\n",
+    "for item in food_shelf:\n",
+    "    if ...:\n",
+    "        print(item, \"is dairy\")\n",
+    "    else:\n",
+    "        print(item, \"is not dairy\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# CS220: Lecture 15\n",
+    "\n",
+    "\n",
+    "## Learning Objectives\n",
+    "After this lecture you will be able to...\n",
+    "- Open an Excel file and export it to a Comma Separated Value file.\n",
+    "- Open a CSV file in TextEditor/Jupyter and connect the elements of the CSV file to the rows and columns in the spreadsheet.\n",
+    "- Use pre-written Python code to read a CSV file into a list of lists.\n",
+    "- Write Python statements with double list indexing to access any element of a CSV file via a list of lists.\n",
+    "- Write code that answers questions about CSV data by writing for loops on lists of lists."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Reading a CSV"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 1: Store the contents of the CSV file into Python lists"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# adapted from https://automatetheboringstuff.com/chapter14/\n",
+    "import csv\n",
+    "\n",
+    "def process_csv(filename):\n",
+    "    # open the file, its a text file utf-8\n",
+    "    example_file = open(filename, encoding=\"utf-8\")\n",
+    "    \n",
+    "    # prepare it for reading as a CSV object\n",
+    "    example_reader = csv.reader(example_file)\n",
+    "    \n",
+    "    # use the built-in list function to convert this into a list of lists\n",
+    "    example_data = list(example_reader)\n",
+    "    \n",
+    "    # close the file to tidy up our workspace\n",
+    "    example_file.close()\n",
+    "    \n",
+    "    # return the list of lists\n",
+    "    return example_data"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Call the `process_csv` function and store the list of lists in `cs220_csv`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cs220_csv = process_csv('cs220_survey_data.csv')\n",
+    "cs220_csv"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Store the header row into `cs220_header`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cs220_header = cs220_csv[0]\n",
+    "cs220_header"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Store all of the data rows into `cs220_data`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cs220_data = cs220_csv[1:]\n",
+    "cs220_data"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 2: CSVs as a List of Lists"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out the lecture number of the 4th student by hardcoding its row and column"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cs220_data[...][...] # [row][col]"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out the sleeping habit for the 2nd student by hardcoding its row and column"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cs220_data[...][...] "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out how many students completed the survey"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "len(...)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out every student's sleep habits and major"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in range(len(cs220_data)):\n",
+    "    current_sleep_habit = ...\n",
+    "    current_major = ...\n",
+    "    print(current_sleep_habit + '\\t\\t' + current_major)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out every students' age in 10 years\n",
+    "\n",
+    "Fix the bug in the code below"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in range(...):\n",
+    "    current_age = cs220_data[i][2]\n",
+    "    print(current_age + 10)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## It would be nice to have a helper function!\n",
+    "Let's introduce `cell`"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Remember creating `cs220_header`?"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cs220_header"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Get the column index of `\"Pizza topping\"`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cs220_header.index(...)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 3: Create a `cell` function\n",
+    "\n",
+    "We want to invoke something like...\n",
+    "* `cell(24, \"Pet owner\")`\n",
+    "* `cell(63, \"Zip Code\")`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def cell(row_idx, col_name):\n",
+    "    col_idx = ... # get the index of col_name\n",
+    "    val = ...     # get the value of cs220_data at the specified cell\n",
+    "    return val"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out the lecture number of the 4th student using the `cell` function"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "cell(..., ...)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out every student's sleep habits and major using the `cell` function"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in range(len(cs220_data)):\n",
+    "    current_sleep_habit = ...\n",
+    "    current_major = ...\n",
+    "    print(current_sleep_habit + '\\t\\t' + current_major)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out every students' age in 10 years using the `cell` function\n",
+    "\n",
+    "This does not quite work. Fix this code:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in range(len(cs220_data)):\n",
+    "    current_age = cell(i, \"Age\")\n",
+    "    if current_age != None:\n",
+    "        print(current_age + 10)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 4: Improve the `cell` function \n",
+    "\n",
+    "Improve the `cell` function so it returns the appropriate type. If there is **nothing** in the cell, return `None`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def cell(row_idx, col_name):\n",
+    "    col_idx = cs220_header.index(col_name)\n",
+    "    val = cs220_data[row_idx][col_idx]\n",
+    "    if ...:\n",
+    "        return None\n",
+    "    elif ...:\n",
+    "        return int(val)\n",
+    "    else:\n",
+    "        return val"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Print out every student's sleep habits and major using the `cell` function"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in range(len(cs220_data)):\n",
+    "    current_age = cell(i, \"Age\")\n",
+    "    if current_age != None:\n",
+    "        print(current_age + 10)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 5: Get the average age of each lecture"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "students_lec_001 = []\n",
+    "students_lec_002 = []\n",
+    "students_lec_003 = []\n",
+    "students_lec_004 = []\n",
+    "students_lec_005 = []\n",
+    "for i in range(len(cs220_data)):\n",
+    "    current_lec = ...\n",
+    "    current_age = ...\n",
+    "    if ...: # TODO: check for missing data\n",
+    "        continue\n",
+    "    if current_lec == \"LEC001\":\n",
+    "        students_lec_001.append(current_age)\n",
+    "    elif current_lec == \"LEC002\":\n",
+    "        students_lec_002.append(current_age)\n",
+    "    elif current_lec == \"LEC003\":\n",
+    "        students_lec_003.append(current_age)\n",
+    "    elif current_lec == \"LEC004\":\n",
+    "        students_lec_004.append(current_age)\n",
+    "    elif current_lec == \"LEC005\":\n",
+    "        students_lec_005.append(current_age)\n",
+    "            \n",
+    "print(\"Average age for LEC001 is\", round(sum(students_lec_001) / len(students_lec_001), 2))\n",
+    "print(\"Average age for LEC002 is\", round(sum(students_lec_002) / len(students_lec_002), 2))\n",
+    "print(\"Average age for LEC003 is\", round(sum(students_lec_003) / len(students_lec_003), 2))\n",
+    "print(\"Average age for LEC004 is\", round(sum(students_lec_004) / len(students_lec_004), 2))\n",
+    "print(\"Average age for LEC005 is\", round(sum(students_lec_005) / len(students_lec_005), 2))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Bonus challenge: Can you do this with a little less hardcoding?"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "lectures_of_ages = [\n",
+    "    [],\n",
+    "    [],\n",
+    "    [],\n",
+    "    [],\n",
+    "    []\n",
+    "]\n",
+    "for i in range(len(cs220_data)):\n",
+    "    current_lec = int(cell(i, \"Lecture\")[-1]) - 1 # Will be a number 0 - 4\n",
+    "    current_age = cell(i, \"Age\")\n",
+    "    if current_age != None:\n",
+    "        lectures_of_ages[current_lec].append(current_age)\n",
+    "\n",
+    "# TODO: Print the average ages"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Example 6: What are the unique ages for each lecture?"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in range(len(lectures_of_ages)):\n",
+    "    ages_of_lecture_i = ...\n",
+    "    unique_ages = ...\n",
+    "    print(unique_ages)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## You try!"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Complete the challenges below. First try completing the problem directly using the list of lists (e.g. double indexing `[][]`), then try using the `cell` function!"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Exercise 1: Of all runners, how many are procrastinators? "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Exercise 2: What percentage of 18-year-olds have their major declared as \"Other\"?"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Exercise 3: Does the oldest basil/spinach-loving Business major prefer cats, dogs, or neither?"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.11.7"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}