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  {
   "cell_type": "markdown",
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   "source": [
    "# Loops and Conditionals \n",
    "\n",
    "### Other resources\n",
    "\n",
    "Python course at https://codecademy.com\n",
    "\n",
    "Python flow control tutorial https://docs.python.org/3/tutorial/controlflow.html "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Loops"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The `range()` command offers an easy way to loop over a sequence of numbers.  Remember that Python is 0 indexed."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n",
      "6\n",
      "7\n",
      "8\n",
      "9\n"
     ]
    }
   ],
   "source": [
    "for i in range(10):\n",
    "    print(i)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can also loop over anything that is iterable, this includes lists, tuples, and dictonaries."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "alist = ['a', 'b', 'c']"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In the loop below `aletter` takes on each value of `alist` every cycle through the loop."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a\n",
      "b\n",
      "c\n"
     ]
    }
   ],
   "source": [
    "for aletter in alist:\n",
    "    print(aletter)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "There are also `while`-loops, but the syntax is not as clear as `for`-loops and there is always a danger of entering an infinite loop."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n",
      "6\n",
      "7\n",
      "8\n",
      "9\n",
      "10\n"
     ]
    }
   ],
   "source": [
    "i=0\n",
    "mybool = False\n",
    "while mybool is not True:\n",
    "    print(i)\n",
    "    i += 1\n",
    "    if i > 10:\n",
    "        mybool = True"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "I prefer `for`-loops with a fixed number of iterations and a `break` statement to replicate the logic of `while`-loops, but protecting from infinite cycles."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n",
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      "8\n",
      "9\n",
      "10\n",
      "11\n"
     ]
    }
   ],
   "source": [
    "for i in range(100):\n",
    "    print(i)\n",
    "    \n",
    "    if i > 10:\n",
    "        break"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Here is an example of a conditional statement with `and` or `or` logic."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n",
      "6\n",
      "7\n",
      "8\n",
      "9\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "Hello!\n",
      "21\n",
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      "98\n",
      "99\n"
     ]
    }
   ],
   "source": [
    "for i in range(100):\n",
    "    \n",
    "    if i < 10 or i > 20:\n",
    "        print(i)\n",
    "    else:\n",
    "        print(\"Hello!\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python offers a clean syntax for testing if an item is stored in a list, tuple, or dictionary."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True!!!!\n"
     ]
    }
   ],
   "source": [
    "alist = ['a', 'b', 'c']\n",
    "\n",
    "if 'd' not in alist:\n",
    "    print(\"True!!!!\")\n",
    "else:\n",
    "    print(\"False!!!!\")"
   ]
  }
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