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   "source": [
    "<h1>2. Lists and Dictionaries</h1>\n",
    "<h2>10/02/23</h2>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<h2>2.0 Last Time...</h2>\n",
    "\n",
    "<ul>\n",
    "    <li>Python has a variety of data types, many of which we saw today!</li>\n",
    "    <li>An <b>integer</b> variable is a number with no decimal point.</li>\n",
    "    <li>A <b>floating point</b> variable is a number with a decimal point</li>\n",
    "    <li>A <b>string</b> variable is text.</li>\n",
    "    <li>A <b>Boolean</b> variable can take on the values <b>True</b> and <b>False</b>.</li>\n",
    "    <li>A <b>NoneType</b> variable can take on the value <b>None</b>.</li>\n",
    "    <li>Python uses dynamic typing, which means you don't need to define a variable's type when you first use that variable.</li>\n",
    "    <li>The type() command lets you see what type a given variable is. int(), float(), and str() can be used to convert to different variable types.</li>\n",
    "    <li>Combining a float and an integer results in a float.</li>\n",
    "    <li>Combining a string and an integer or float results in a TypeError.</li>\n",
    "    <li>Floats are often prone to rounding errors.</li>\n",
    "    <li><b>and</b> and <b>or</b> can be used to combine Boolean variables.</li>\n",
    "</ul>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<h2>2.1 Lists and Tuples</h2>\n",
    "\n",
    "A <b>list</b> is simply an ordered sequence of values, similar to arrays in other programming languages. Each element of a list can be assigned to anything (you can have a mix of variable types within a given list), including another list.\n",
    "\n",
    "Lists are defined using square brackets (\"[]\"), and individual elements have commas between them.\n",
    "\n",
    "Counting in Python starts with <b>0</b>. This can lead to some confusion, but always remember that the first element in a list is actually element 0, the second is actually element 1, and so on.\n",
    "\n",
    "You can also count from the end, so that element <b>-1</b> is actually the last element in a list, <b>-2</b> is the second-last element, and so on.\n",
    "\n",
    "Finally, to find the length of a list, use the len() command."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Create a complicated list that has a list as one of its elements.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# As a side note, if you want to split a long line of code across\n",
    "# multiple lines, just use a backslash with nothing after it:\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Find the length of this list.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# To get a value from a list within a list:\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Likewise, you can make use of the reverse numbering:\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "A list can be sliced to just obtain a subsection using a colon to separate the lower and upper limits. The lower limit of the range is <b>inclusive</b> and the upper range is <b>exclusive</b>, so that a [1:3] subset will consist of the second and third elements in a list."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Values within a list can be changed; lists are <b>mutable</b>. Changing by assignment is the most basic way to do this."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Let's change 'hello' to 'goodbye' in the original list.\n",
    "\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Lists in python actually have some built-in functions called <b>methods</b> that can change the properties of the list. We'll talk about these more when we get into object-oriented programming later in this course, but for now, we'll consider <b>insert</b>, <b>remove</b> and <b>append</b>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# 'Insert' places the requested element into the list \n",
    "# before the specified element of the list.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# 'Remove' gets rid of the first occurrence of the specified element.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Append adds the specified element to the end of the list.\n",
    "\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To an extent, you can treat an individual string as a list."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "A <b>tuple</b> is simply a list that cannot be changed (i.e., <b>immutable</b>), and an error will be returned by Python if you do attempt to change an element within a tuple. Defining a tuple is exactly the same as defining a list, except that you use parentheses instead of square brackets."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Create a simple tuple:\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# But note that you cannot change a value within a tuple.\n",
    "\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<h2>2.2 Dictionaries</h2>\n",
    "\n",
    "A dictionary, as opposed to a list/tuple, is an <b>unordered</b> list: elements are referenced by <b>keys</b>, not position. A key can be anything, as can the value it refers to.\n",
    "\n",
    "A dictionary is delimited by curly braces (\"{}\"), and each element is a key:value pair separated by a colon. In order to refer to a particular element in a dictionary, we proceed much as we do with a list, except using a key instead of an element address."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Let's create a dictionary similar to our list from earlier.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Here, our keys are 'value_a','value_b',and 'value_c', and we can refer to \n",
    "# each of them accordingly.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Just like lists, dictionaries have <b>methods</b> - and again, we'll go over this in more detail as we get to the object-oriented programming part of this course, but for now, consider <b>keys</b> and <b>values</b>."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# \"Keys\" returns a list of all the keys of a.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# \"Values\" returns a list of all the values of a.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# To check whether a particular key is used in a dictionary, use the following\n",
    "# syntax:\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Note that <b>keys</b> and <b>values</b> will return key:value pairs in no particular order. To make sure one corresponds to the other, you can first sort the dictionary into a desired order using something like <b>sorted</b>, which we'll explore soon."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<h1>TAKE-HOME POINTS</h1>\n",
    "\n",
    "<ul>\n",
    "    <li>A list is a <b>mutable</b>, <b>ordered</b> sequence of elements.</li>\n",
    "    <li>Python counts starting with 0, not 1.</li>\n",
    "    <li>You can also count backwards from the end of a list using negative numbers.</li>\n",
    "    <li>A list can be sliced, where the slice is defined by a range that has an inclusive lower bound and an exclusive upper bound.</li>\n",
    "    <li>Values in a list can be changed by assignment or by particular methods.</li>\n",
    "    <li>A tuple is an <b>immutable</b>, <b>ordered</b> sequence of elements.</li>\n",
    "    <li>A dictionary is a <b>mutable</b>, <b>unordered</b> sequence of elements consisting of key:value pairs.</li>\n",
    "</ul>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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