04_python_sets.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Set Data Structure Cheat Sheet\n",
    "\n",
    "This cheat sheet contains everything related to List DS.\n",
    "\n",
    "Set is unordered collection of items, mutable, used to perform mathematical operations"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<class 'set'>\n"
     ]
    }
   ],
   "source": [
    "s = {1,2,3,4}\n",
    "print(type(s))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{1, 2, 3, 4}\n"
     ]
    }
   ],
   "source": [
    "s = {1,2,3,4,4,4,4,4,4,4,4,4,4}\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{1, 2, 3, 4, 5}\n"
     ]
    }
   ],
   "source": [
    "s = set([1,2,2,3,3,4,4,5,5])\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{1, 2, 3, 4}\n",
      "{1, 2, 3, 4, 5, 6, 7}\n",
      "{1, 2, 3, 4, 5, 6, 7, 1123, 11, 112}\n"
     ]
    }
   ],
   "source": [
    "# Add elements to a set\n",
    "\n",
    "s = {1,2,3}\n",
    "# print(s[1])   Indexing not possible\n",
    "\n",
    "s.add(4)\n",
    "print(s)\n",
    "\n",
    "# Add multiple elements\n",
    "s.update([5,6,7])\n",
    "print(s)\n",
    "\n",
    "\n",
    "# Add lists and set\n",
    "s.update([5,6,7], {11,11,11,112,1123})\n",
    "print(s)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{1, 2, 3, 5}\n"
     ]
    }
   ],
   "source": [
    "# Remove elements\n",
    "# clear() to remove all the elements\n",
    "s = {1,2,3,4,5}\n",
    "\n",
    "s.discard(4)\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{1, 3, 5}\n"
     ]
    }
   ],
   "source": [
    "s.remove(2)\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "ename": "KeyError",
     "evalue": "2",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mKeyError\u001b[0m                                  Traceback (most recent call last)",
      "\u001b[1;32m<ipython-input-9-19f841fb8ee4>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0ms\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0mremove\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;36m2\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0ms\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n",
      "\u001b[1;31mKeyError\u001b[0m: 2"
     ]
    }
   ],
   "source": [
    "s.remove(2)\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{1, 3, 5}\n"
     ]
    }
   ],
   "source": [
    "s.discard(2)\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{3, 5}\n"
     ]
    }
   ],
   "source": [
    "# pop() also used to remove\n",
    "\n",
    "s.pop()   # Random element is removes\n",
    "\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Pyhton Set operations"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{1, 2, 3, 4, 5, 6, 7}\n",
      "{1, 2, 3, 4, 5, 6, 7}\n",
      "{3, 4, 5}\n",
      "{3, 4, 5}\n",
      "{1, 2}\n",
      "{1, 2}\n",
      "{1, 2, 6, 7}\n",
      "{1, 2, 6, 7}\n",
      "False\n",
      "True\n"
     ]
    }
   ],
   "source": [
    "set1 = {1,2,3,4,5}\n",
    "set2 = {3,4,5,6,7}\n",
    "\n",
    "#union of 2 sets using | operator\n",
    "\n",
    "print(set1 | set2)\n",
    "\n",
    "#another way\n",
    "print(set1.union(set2))\n",
    "\n",
    "# Intersection\n",
    "print(set1 & set2)\n",
    "\n",
    "#use intersection function \n",
    "print(set1.intersection(set2))\n",
    "\n",
    "#set Difference\n",
    "print(set1 - set2)\n",
    "\n",
    "#use differnce function \n",
    "print(set1.difference(set2))\n",
    "\n",
    "# symmetric difference: set of elements in both set1 and set2 except those that are common in both\n",
    "\n",
    "#use ^ operator\n",
    "\n",
    "print(set1^set2)\n",
    "\n",
    "#use symmetric_difference function\n",
    "print(set1.symmetric_difference(set2))\n",
    "\n",
    "#find issubset()\n",
    "x = {\"a\",\"b\",\"c\",\"d\",\"e\"}\n",
    "y = {\"c\",\"d\"}\n",
    "\n",
    "print(x.issubset(y))\n",
    "print(y.issubset(x))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Frozen Set\n",
    "\n",
    "Frozen sets has the characteristics of sets, but we can't be changed once it's assigned. While tuple are immutable lists, frozen sets are immutable sets\n",
    "\n",
    "Sets being mutable are unhashable, so they can't be used as dictionary keys. On the other hand, frozensets are hashable and can be used as keys to a dictionary.\n",
    "\n",
    "This datatype supports methods like copy(), difference(), intersection(), isdisjoint(), issubset(), issuperset(), symmetric_difference() and union(). Being immutable it does not have method that add or remove elements.\n",
    "\n",
    "Frozensets can be created using the function frozenset()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "'frozenset' object has no attribute 'add'",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[1;32m<ipython-input-14-d68927fcc176>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m      2\u001b[0m \u001b[0mset2\u001b[0m \u001b[1;33m=\u001b[0m \u001b[0mfrozenset\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;36m3\u001b[0m\u001b[1;33m,\u001b[0m\u001b[1;36m4\u001b[0m\u001b[1;33m,\u001b[0m\u001b[1;36m5\u001b[0m\u001b[1;33m,\u001b[0m\u001b[1;36m6\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      3\u001b[0m \u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 4\u001b[1;33m \u001b[0mset1\u001b[0m\u001b[1;33m.\u001b[0m\u001b[0madd\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;36m7\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;31mAttributeError\u001b[0m: 'frozenset' object has no attribute 'add'"
     ]
    }
   ],
   "source": [
    "set1 = frozenset([1,2,3,4])\n",
    "set2 = frozenset([3,4,5,6])\n",
    "\n",
    "set1.add(7)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "ename": "TypeError",
     "evalue": "'frozenset' object does not support indexing",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[1;32m<ipython-input-15-be32ec393e2f>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mset1\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;36m1\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[1;31mTypeError\u001b[0m: 'frozenset' object does not support indexing"
     ]
    }
   ],
   "source": [
    "print(set1[1])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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