{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "tribal-chrome",
   "metadata": {},
   "source": [
    "# Iterators and Generators (21/4 - 2021)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "faced-cornell",
   "metadata": {},
   "source": [
    "## Exercise\n",
    "\n",
    "Create an iterable class ``arange(start, end, step)`` to return values start, start + step, start + 2 * step, ..."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "id": "strange-piano",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1\n",
      "2\n",
      "3\n",
      "4\n"
     ]
    }
   ],
   "source": [
    "L = [1, 2, 3, 4]  # iterabel\n",
    "#       ^\n",
    "#       | iterator\n",
    "\n",
    "for x in L:\n",
    "    print(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "id": "trying-watershed",
   "metadata": {
    "scrolled": true
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<class 'list'>\n",
      "<class 'list_iterator'>\n"
     ]
    }
   ],
   "source": [
    "L = [1,2,3]\n",
    "\n",
    "print(type(L))\n",
    "print(type(iter(L)))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "id": "blocked-cycling",
   "metadata": {
    "scrolled": true
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a\n",
      "b\n",
      "c\n",
      "d\n"
     ]
    },
    {
     "ename": "StopIteration",
     "evalue": "",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mStopIteration\u001b[0m                             Traceback (most recent call last)",
      "\u001b[1;32m<ipython-input-14-59304fd29e7a>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m\u001b[0m\n\u001b[0;32m      5\u001b[0m \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mnext\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mit\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      6\u001b[0m \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mnext\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mit\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 7\u001b[1;33m \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mnext\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mit\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;31mStopIteration\u001b[0m: "
     ]
    }
   ],
   "source": [
    "L = ['a', 'b', 'c', 'd']  # iterabel\n",
    "it = iter(L)\n",
    "print(next(it))\n",
    "print(next(it))\n",
    "print(next(it))\n",
    "print(next(it))\n",
    "print(next(it))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "id": "unlimited-sarah",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<list_iterator object at 0x00000235C9549790>\n"
     ]
    }
   ],
   "source": [
    "L = ['a', 'b', 'c', 'd']  # iterabel\n",
    "print(L.__iter__())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "id": "welsh-steps",
   "metadata": {},
   "outputs": [],
   "source": [
    "class arange:  # iterabel\n",
    "    def __init__(self, start, end, step):\n",
    "        self.start = start\n",
    "        self.end = end\n",
    "        self.step = step\n",
    "    \n",
    "    def __iter__(self):  # skal returnere en iterator\n",
    "        return arange_iterator(self)\n",
    "    \n",
    "    def __repr__(self):\n",
    "        return f'arange({self.start}, {self.end}, {self.step})'\n",
    "    \n",
    "class arange_iterator:\n",
    "    def __init__(self, arange_object):\n",
    "        self.arange_object = arange_object\n",
    "        self.value = self.arange_object.start\n",
    "        \n",
    "    def __next__(self):\n",
    "        if self.value >= self.arange_object.end:\n",
    "            raise StopIteration\n",
    "        answer = self.value\n",
    "        self.value += self.arange_object.step\n",
    "        return answer"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "id": "capital-scanner",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "10\n",
      "10.3\n",
      "10.600000000000001\n",
      "10.900000000000002\n",
      "11.200000000000003\n",
      "11.500000000000004\n",
      "11.800000000000004\n"
     ]
    }
   ],
   "source": [
    "#r = arange(10, 20, .3)\n",
    "r = arange(10, float('inf'), .3)\n",
    "\n",
    "#it = iter(r)\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "\n",
    "for i, x in enumerate(r):\n",
    "    print(x)\n",
    "    if i > 5:\n",
    "        break"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 65,
   "id": "acoustic-violence",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "arange(3, 5, 0.25)"
      ]
     },
     "execution_count": 65,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "arange(3, 5, 0.25)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 69,
   "id": "distinct-notification",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[9, 10.5625, 12.25, 14.0625, 16.0, 18.0625, 20.25, 22.5625]"
      ]
     },
     "execution_count": 69,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[x ** 2 for x in arange(3, 5, 0.25)]"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "horizontal-offset",
   "metadata": {},
   "source": [
    "## Exercise\n",
    "\n",
    "Generator expression to create powers of two."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 86,
   "id": "complex-infrastructure",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[0, 1, 4, 9, 16]\n"
     ]
    }
   ],
   "source": [
    "g = (x ** 2 for x in range(5))\n",
    "print(list(g))\n",
    "\n",
    "#h = (x + 1 for x in g)\n",
    "\n",
    "#print(list(h))\n",
    "\n",
    "#it = iter(g)\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "#print(next(it))\n",
    "\n",
    "#print(type(g))\n",
    "#for x in g:\n",
    "#    print(x)\n",
    "\n",
    "#print(sum(g))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 93,
   "id": "illegal-minister",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1023\n",
      "1023\n",
      "1023\n"
     ]
    }
   ],
   "source": [
    "powers_of_two = (2 ** i for i in range(10))\n",
    "\n",
    "print(sum(powers_of_two))\n",
    "print(sum( (2 ** i for i in range(10)) ))\n",
    "print(sum(2 ** i for i in range(10)))"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "sized-bulgaria",
   "metadata": {},
   "source": [
    "## Exercise\n",
    "\n",
    "Create generator ``g(n)`` to generate all pairs (x, y) where x and y are from range(n) and x + y is not divisble by 3."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 112,
   "id": "controversial-purchase",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "(0, 1)\n",
      "(0, 2)\n",
      "(1, 0)\n",
      "(1, 1)\n",
      "(2, 0)\n",
      "(2, 2)\n"
     ]
    }
   ],
   "source": [
    "def g(n):\n",
    "    for x in range(n):\n",
    "        for y in range(n):\n",
    "            if (x + y) % 3 != 0:\n",
    "                yield (x, y)\n",
    "     \n",
    "\n",
    "for value in g(3):\n",
    "    print(value)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 116,
   "id": "arranged-drill",
   "metadata": {},
   "outputs": [],
   "source": [
    "def arange(start, slut, step):\n",
    "    value = start\n",
    "    while value < slut:\n",
    "        yield value\n",
    "        value += step\n",
    "    \n",
    "r = arange(3, 6, 0.25)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 117,
   "id": "opposite-shadow",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[3, 3.25, 3.5, 3.75, 4.0, 4.25, 4.5, 4.75, 5.0, 5.25, 5.5, 5.75]\n"
     ]
    }
   ],
   "source": [
    "print(list(r))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "regulated-distribution",
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3",
   "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": "3.9.4"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}