session-six/session_six_filled_template.ipynb

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    "<a href=\"https://colab.research.google.com/github/warwickdatascience/beginners-python/blob/master/session_six/session_six_filled_template.ipynb\" target=\"_parent\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/></a>"
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   "source": [
    "<center>Spotted a mistake? Report it <a href=\"https://github.com/warwickdatascience/beginners-python/issues/new\">here</a></center>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Beginner's Python—Session Six Template"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "-Ceh1HnZIsVO"
   },
   "source": [
    "## Functions"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "colab_type": "text",
    "id": "6AZ6H-6jKoSt"
   },
   "source": [
    "### Introduction\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Confirm that the type of `print` is `builtin_function_or_method`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "colab": {
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    "id": "D4l_2DsZIlgB",
    "outputId": "e63ad5b1-2062-4d8c-9ee7-b03a25d72001"
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "builtin_function_or_method"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "type(print)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
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    "colab_type": "code",
    "id": "9lLW387eKgNN",
    "outputId": "860dcf3b-f3e5-402d-f58f-4d28fb69a6b1"
   },
   "source": [
    "Create a function that will print text when ran and run it twice"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "colab": {
     "base_uri": "https://localhost:8080/",
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    },
    "colab_type": "code",
    "id": "bIr0l5kJI_VV",
    "outputId": "c7891804-4acf-4856-e51a-271914a8dc60"
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello, World!\n",
      "Once more?\n",
      "Hello, World!\n"
     ]
    }
   ],
   "source": [
    "def say_hello():\n",
    "    print(\"Hello, World!\")\n",
    "\n",
    "say_hello()\n",
    "print(\"Once more?\")\n",
    "say_hello()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function which returns a number and run it, storing the returned value in a variable"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "5\n"
     ]
    }
   ],
   "source": [
    "def five():\n",
    "    return 5\n",
    "\n",
    "num = five()\n",
    "print(num)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Standard Puzzles"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to print the string 'Hello!' and run this"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [],
   "source": [
    "def greet():\n",
    "    print(\"Hello\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function which calls the above function five times"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello\n",
      "Hello\n",
      "Hello\n",
      "Hello\n",
      "Hello\n"
     ]
    }
   ],
   "source": [
    "def greet_group():\n",
    "    for i in range(5):\n",
    "        greet()\n",
    "\n",
    "greet_group()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to calculate and return the value of $2 + 2$"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4\n"
     ]
    }
   ],
   "source": [
    "def two_plus_two():\n",
    "    return 2 + 2\n",
    "\n",
    "four = two_plus_two()\n",
    "print(four)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Function Arguments"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Introduction"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to square an inputted number"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "9\n"
     ]
    }
   ],
   "source": [
    "def square(num):\n",
    "    print(num ** 2)\n",
    "    \n",
    "square(3)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to add two numbers, with the second parameter taking a default value of $1$"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [],
   "source": [
    "def add(a, b=1):\n",
    "    print(a + b)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Standard Puzzles"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to greet a named person, with fallback default behaviour"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [],
   "source": [
    "def greet_person(name='unknown'):\n",
    "    if name == 'unknown':\n",
    "        print(\"Hello. What's your name?\")\n",
    "    else:\n",
    "        print(\"Hello,\", name)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to calculate the area of a rectangle"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [],
   "source": [
    "def rectangle_area(width, height):\n",
    "    return width * height"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Bonus Puzzles"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Improve the greeter function above by using `None` as the default value for the name parameter"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [],
   "source": [
    "def greet_person(name=None):\n",
    "    if name is None:\n",
    "        print(\"Hello. What's your name?\")\n",
    "    else:\n",
    "        print(\"Hello,\", name)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Recursion"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Introduction"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to calculate the nth Fibonacci number using recursion"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "89"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def fibonacci(n):\n",
    "    if n == 0 or n == 1:\n",
    "        return 1\n",
    "    return fibonacci(n-1) + fibonacci(n-2)\n",
    "\n",
    "fibonacci(10)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Standard Puzzles"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create a function to calculate $n!$ using recursion"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "24"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def factorial(n):\n",
    "    if n == 1:\n",
    "        return 1\n",
    "    return n * factorial(n-1)\n",
    "\n",
    "factorial(4)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Bonus Puzzles"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Refactor the above function using an iterative paradigm"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "24"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def factorial(n):\n",
    "    prod = 1\n",
    "    for i in range(2, n + 1):\n",
    "        prod *= i\n",
    "    return prod\n",
    "\n",
    "factorial(4)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Variable Scope"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Introduction"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "_The examples given in the presentation are not the most suitable to use as exercises, so instead just make sure you've gave them a good look over_"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Standard Puzzles"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Predict what values will be printed when running the presentation code. Verify this"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The results will be 10 and 2 respectively. THe first prints the local variable `a` whereas the second prints the global variable"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "10\n",
      "2\n"
     ]
    }
   ],
   "source": [
    "a = 2\n",
    "\n",
    "def double(b):\n",
    "    a = b * 2\n",
    "    print(a)\n",
    "    \n",
    "double(5)\n",
    "print(a)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Rewrite the supplied code to avoid referencing global variables"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "100\n"
     ]
    }
   ],
   "source": [
    "n = 10\n",
    "\n",
    "def square(n):\n",
    "    return n ** 2\n",
    "\n",
    "print(square(n))"
   ]
  }
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