{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Iterator Pattern\n",
    "1. Standard way to iterate over a collection\n",
    "1. Also Known as **Cursor Pattern**"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Collection of Employees"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 1. Using Collections"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "from collections import Iterable, Iterator"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "class EmployeesIterator(Iterator):\n",
    "    def __init__(self, employees, head_count):\n",
    "        self._employees = employees\n",
    "        self._head_count = head_count\n",
    "        self._emp_id = 0\n",
    "        \n",
    "    def __iter__(self):\n",
    "        return self\n",
    "    \n",
    "    def __next__(self):\n",
    "        if self._emp_id < self._head_count:\n",
    "            self._emp_id += 1\n",
    "            return self._employees[self._emp_id]\n",
    "        else:\n",
    "            raise StopIteration"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "class Employees(Iterable):\n",
    "    _employees = {}\n",
    "    _head_count = 0\n",
    "    _emp_id = 0\n",
    "    \n",
    "    def add_employee(self, emp_id, employee):\n",
    "        self._head_count += 1\n",
    "        self._emp_id = emp_id\n",
    "        self._employees[self._emp_id] = employee\n",
    "        \n",
    "    def __iter__(self):\n",
    "        return EmployeesIterator(self._employees, self._head_count)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "test_employees = ['Ashutosh', 'Bipender', 'Sameer', 'Abhijit']\n",
    "\n",
    "employees = Employees()\n",
    "\n",
    "for i, emp in enumerate(test_employees):\n",
    "    employees.add_employee(i + 1, emp)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "scrolled": true
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Ashutosh\n",
      "Bipender\n",
      "Sameer\n",
      "Abhijit\n"
     ]
    }
   ],
   "source": [
    "for e in employees:\n",
    "    print(e)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Using Generators"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "class Employees(Iterable):\n",
    "    _employees = {}\n",
    "    _head_count = 0\n",
    "    _emp_id = 0\n",
    "    \n",
    "    def add_employee(self, emp_id, employee):\n",
    "        self._head_count += 1\n",
    "        self._emp_id = emp_id\n",
    "        self._employees[self._emp_id] = employee\n",
    "        \n",
    "    def __iter__(self):    # Or - return (e for e in self._employees.values())\n",
    "        for i in range(self._head_count):\n",
    "            yield self._employees[i + 1]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "employees = Employees()\n",
    "\n",
    "for i, emp in enumerate(test_employees):\n",
    "    employees.add_employee(i + 1, emp)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\"Ashutosh\"\n",
      "\"Bipender\"\n",
      "\"Sameer\"\n",
      "\"Abhijit\"\n"
     ]
    }
   ],
   "source": [
    "for e in employees:\n",
    "    print(f'\"{e}\"')"
   ]
  }
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