itertools_module.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<h1 align=\"center\">Itertools module</h1>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import starmap\n",
    "\n",
    "evaluated_values = starmap(lambda x, y: x + x, [(1, 2), (3, 4), (5, 6), (7, 8)])\n",
    "for i in evaluated_values:\n",
    "    print(i, end = ' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import zip_longest\n",
    "\n",
    "print(list(zip_longest([1, 2, 3], [11, 12], [21, 22, 23, 25], [31, 32])))\n",
    "print(list(zip_longest([1, 2, 3], [11, 12], [21, 22, 23, 25], [31, 32], fillvalue = -1)))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from operator import mul\n",
    "from itertools import accumulate\n",
    "\n",
    "print(tuple(accumulate([0, 1, 2, 3, 4, 5])))\n",
    "print(tuple(accumulate([1, 2, 3, 4, 5], mul)))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import combinations\n",
    "\n",
    "print(list(combinations(range(4), 0)))\n",
    "print(tuple(combinations(range(4), 2)))\n",
    "print(set(combinations(range(4), 4)))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import combinations_with_replacement\n",
    "\n",
    "print(list(combinations_with_replacement(range(4), 1)))\n",
    "print(tuple(combinations_with_replacement(range(4), 2)))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import permutations\n",
    "\n",
    "print(list(permutations(range(4), 0)))\n",
    "print(tuple(permutations(range(4), 2)))\n",
    "print(set(permutations(range(4))))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import product\n",
    "\n",
    "for i in product(range(3), range(2), range(4)):\n",
    "    print(i)\n",
    "print()\n",
    "\n",
    "for i in product(range(2), repeat = 4):\n",
    "    print(i)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import count\n",
    "\n",
    "# Arguments \"start\" and \"step\" take default values of 0 and 1, respectively.\n",
    "counter = count()\n",
    "for i in counter:\n",
    "    if i > 9:\n",
    "        break\n",
    "    print(i, end = ' ')\n",
    "print()\n",
    "\n",
    "counter = count(10)\n",
    "for i in counter:\n",
    "    if i > 19:\n",
    "        break\n",
    "    print(i, end = ' ')\n",
    "print()\n",
    "\n",
    "counter = count(10, 2)\n",
    "for i in counter:\n",
    "    if i > 19:\n",
    "        break\n",
    "    print(i, end = ' ')\n",
    "print()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import tee\n",
    "\n",
    "copies = tee(range(4))\n",
    "for i in copies:\n",
    "    print(list(i))\n",
    "print()\n",
    "\n",
    "copies = tee(range(4), 5)\n",
    "for i in copies:\n",
    "    print(list(i))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import repeat\n",
    "\n",
    "to_be_repeated = repeat(range(3))\n",
    "for i in range(6):\n",
    "    print(set(next(to_be_repeated)), end = ' ')\n",
    "print()\n",
    "\n",
    "to_be_repeated = repeat(range(3), 6)\n",
    "for i in to_be_repeated:\n",
    "    print(set(i), end = ' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import cycle\n",
    "\n",
    "values_to_cycle_over = cycle(range(4))\n",
    "for i in range(10):\n",
    "    print((i, next(values_to_cycle_over)), end = ' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import chain\n",
    "\n",
    "for i in chain([1, 2, 3], (4, 5, 6), {7, 8}, {9: 'A', 10: 'B'}):\n",
    "    print(i, end = ' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import compress\n",
    "\n",
    "print(list(compress(range(0, 400, 10), (x > 32 for x in range(40)))))\n",
    "print(list(compress(range(0, 40), [x % y == 0 for y in range(2, 6) for x in range(10)])))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import dropwhile\n",
    "\n",
    "for i in dropwhile(lambda x : x % 3, [1, 4, 5, 2, 9, 3, 6, 0, 8, 7]):\n",
    "    print(i, end = ' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import takewhile\n",
    "\n",
    "for i in takewhile(lambda x : x % 3, [1, 4, 5, 2, 9, 3, 6, 0, 8, 7]):\n",
    "    print(i, end = ' ')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import filterfalse\n",
    "\n",
    "for i in filterfalse(lambda x : x % 3, [1, 4, 5, 2, 9, 3, 6, 0, 8, 7]):\n",
    "    print(i, end = ' ')\n",
    "print()\n",
    "    \n",
    "for i in filterfalse(None, [1, 4, 5, 2, 9, 3, 6, 0, 8, 7]):\n",
    "    print(i, end = ' ')    "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import groupby\n",
    "\n",
    "key_function = lambda x: x % 3\n",
    "# Values with the same key have to be consecutive\n",
    "# in order to be grouped together by \"groupby\"\n",
    "sorted_values = sorted(range(20), key = key_function)\n",
    "groups = groupby(sorted_values, key_function)\n",
    "for (key, group) in groups:\n",
    "    print(key, list(group))\n",
    "print()\n",
    "\n",
    "groups = groupby(sorted_values)\n",
    "for (key, group) in groups:\n",
    "    print(key, list(group))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from itertools import islice\n",
    "\n",
    "selection = islice(range(20), 15)\n",
    "for i in selection:\n",
    "    print(i, end = ' ')\n",
    "print()\n",
    "\n",
    "selection = islice(range(20), 3, 15)\n",
    "for i in selection:\n",
    "    print(i, end = ' ')\n",
    "print()\n",
    "\n",
    "selection = islice(range(20), 3, 15, 2)\n",
    "for i in selection:\n",
    "    print(i, end = ' ')"
   ]
  }
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