courses/Basics-program_flow_and_functions.ipynb

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   "source": [
    "# Basics - program flow, functions\n",
    "This is introdcution to: If statement, for loop and functions.\n",
    "\n",
    "## Solution of Fizz Buzz (http://wiki.c2.com/?FizzBuzzTest)\n",
    "Fizz Buzz well known and well structured assignment. In this tutorial it is used to demonstrated some basic Python concepts."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Iterating:\n",
    "Creation of range of numbers 1-10 as a Python generator follows:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "range(1, 10)"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "range(1,10)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Generator can be converted to a list:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "list(range(1, 10))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "List can be made out of string also:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['a', 'd', 'f', 'a', 's', 'd', 'f', 'a', 's', 'd', 'f']"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "list(\"adfasdfasdf\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Next example demonstrate how to iterate over range of numbers - see printed output to understand the flow:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Start\n",
      "\n",
      "New iteration.\n",
      "The number:  1\n",
      "The number squared:  1\n",
      "Iteration end.\n",
      "\n",
      "New iteration.\n",
      "The number:  2\n",
      "The number squared:  4\n",
      "Iteration end.\n",
      "\n",
      "New iteration.\n",
      "The number:  3\n",
      "The number squared:  9\n",
      "Iteration end.\n",
      "\n",
      "\n",
      "Stop\n"
     ]
    }
   ],
   "source": [
    "print(\"Start\")\n",
    "print()\n",
    "for number in range(1,4):\n",
    "    print(\"New iteration.\")\n",
    "    print(\"The number: \", number)\n",
    "    print(\"The number squared: \", number**2)\n",
    "    print(\"Iteration end.\")\n",
    "    print()\n",
    "print()\n",
    "print(\"Stop\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Modulo\n",
    "To solve Fizz Buzz problem we can utilize the Modulo operation:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "10 % 3"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "50 % 4"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Nice and naive solution\n",
    "The Fizz Buzz solution bellow is totally valid. It is not the most optimal solution, but it is highly readable for humans."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz "
     ]
    }
   ],
   "source": [
    "for number in range(1,100):\n",
    "    if not number % 3 and not number % 5:\n",
    "        print(\"FizzBuzz\", end=\" \")\n",
    "    elif not number % 3:\n",
    "        print(\"Fizz\", end=\" \")\n",
    "    elif not number % 5:\n",
    "        print(\"Buzz\", end=\" \")\n",
    "    else:\n",
    "        print(number, end=\" \")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Ternary operator solution\n",
    "The previous solution can be improved via ternary operator. See explanation below if not clear from following example:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz "
     ]
    }
   ],
   "source": [
    "for number in range(1,100):\n",
    "    text = \"Fizz\" if not number % 3 else \"\"\n",
    "    text = text + \"Buzz\" if not number % 5 else text\n",
    "    text = text if text else number\n",
    "    print(text, end=\" \")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Explanation\n",
    "Ternary operator is basically a \"in line\" if condition that returns value directly."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n"
     ]
    }
   ],
   "source": [
    "text = 1 if False else 0\n",
    "print(text)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## List comprehension\n",
    "Another usefull concept is list comprehension. It is basically an \"in line\" for loop returning container of values. See following regular for loop:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "numbers = []\n",
    "for x in range(10):\n",
    "    numbers.append(x**2)\n",
    "numbers"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now we can replace the example above with list comprehension (it is faster and more readable):"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0,\n",
       " 25,\n",
       " 100,\n",
       " 225,\n",
       " 400,\n",
       " 625,\n",
       " 900,\n",
       " 1225,\n",
       " 1600,\n",
       " 2025,\n",
       " 2500,\n",
       " 3025,\n",
       " 3600,\n",
       " 4225,\n",
       " 4900,\n",
       " 5625,\n",
       " 6400,\n",
       " 7225,\n",
       " 8100,\n",
       " 9025]"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "numbers = [x**2 for x in range(100) if not x % 5]\n",
    "numbers"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can also do a dictionary comprehension (the final prodiuct is dictionary):"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "numbers = {k: k**2 for k in range(10)}\n",
    "numbers"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## While loop\n",
    "In cases we need to iterate till some condition is fulfilled we can use while lopp (this loop does not have fixed number of iterations):"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "27\n"
     ]
    }
   ],
   "source": [
    "N = 1000\n",
    "n = 1\n",
    "while n**2.1 < N:\n",
    "    n += 1\n",
    "print(n)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Fizz Buzz solution with custom print function\n",
    "So far we used Python print function. In the example below, we create custom function to change print behaviour on more than one places:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1 2 Fizz 4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz 22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz 31 32 Fizz 34 Buzz Fizz 37 38 Fizz Buzz 41 Fizz 43 44 FizzBuzz 46 47 Fizz 49 Buzz Fizz 52 53 Fizz Buzz 56 Fizz 58 59 FizzBuzz 61 62 Fizz 64 Buzz Fizz 67 68 Fizz Buzz 71 Fizz 73 74 FizzBuzz 76 77 Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz "
     ]
    }
   ],
   "source": [
    "def better_print(text):\n",
    "    print(text, end=\" \")\n",
    "\n",
    "for number in range(1,100):\n",
    "    if not number % 3 and not number % 5:\n",
    "        better_print(\"FizzBuzz\")\n",
    "    elif not number % 3:\n",
    "        better_print(\"Fizz\")\n",
    "    elif not number % 5:\n",
    "        better_print(\"Buzz\")\n",
    "    else:\n",
    "        better_print(number)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### More functions examples\n",
    "\n",
    "Function are quite usefull concept. More examples follow:\n",
    "- *a* - function that do nothing\n",
    "- *b* - function that returns something\n",
    "- *c* - function that accept input and return output based on input"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [],
   "source": [
    "def a():\n",
    "    pass\n",
    "\n",
    "def b():\n",
    "    return \"Hello world\"\n",
    "\n",
    "def c(word):\n",
    "    return \"Hello {}\".format(word)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [],
   "source": [
    "a()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Hello world'"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "b()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Hello world'"
      ]
     },
     "execution_count": 18,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "c(\"world\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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