loops.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## For loop"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "apple\n",
      "panana\n",
      "orange\n"
     ]
    }
   ],
   "source": [
    "fru = [\"apple\", \"panana\", \"orange\"]\n",
    "for item in fru:\n",
    "    print(item)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Range(start, stop, step) "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 0\n",
      "0 1\n",
      "0 2\n",
      "0 3\n",
      "1 0\n",
      "1 1\n",
      "1 2\n",
      "1 3\n",
      "2 0\n",
      "2 1\n",
      "2 2\n",
      "2 3\n",
      "3 0\n",
      "3 1\n",
      "3 2\n",
      "3 3\n"
     ]
    }
   ],
   "source": [
    "rows, cols = range(0, 4, 1), range(0, 4, 1)\n",
    "\n",
    "for row in rows: \n",
    "    for col in cols:\n",
    "        print(row, col)\n",
    "        "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 -1 -2 -3 -4 -5 -6 -7 -8 -9 "
     ]
    }
   ],
   "source": [
    "for number in range(0, -10, -1):\n",
    "    print(number, end = \" \")\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 2 4 6 8 "
     ]
    }
   ],
   "source": [
    "for number in range(0, 10, 2):\n",
    "    print(number, end = \" \")\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## While loop"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 1 2 3 4 5 6 7 8 9 "
     ]
    }
   ],
   "source": [
    "a, b = 0, 10\n",
    "\n",
    "while a < b:\n",
    "    print(a, end = ' ')\n",
    "    a += 1\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Loop Controls"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "word = 'python'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "p y t h "
     ]
    }
   ],
   "source": [
    "i = 0\n",
    "while i < len(word):\n",
    "    letter = word[i]\n",
    "    i += 1\n",
    "\n",
    "    if letter == 'o':\n",
    "        break # stop iter\n",
    "\n",
    "    print(letter, end = \" \")    \n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "p y h o n "
     ]
    }
   ],
   "source": [
    "i = 0\n",
    "while i < len(word):\n",
    "    letter = word[i]\n",
    "\n",
    "    i += 1\n",
    "\n",
    "    if letter == 't':\n",
    "        continue # jump to next iter\n",
    "    \n",
    "    print(letter, end = \" \")\n",
    "    "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "p y t h o n "
     ]
    }
   ],
   "source": [
    "i = 0\n",
    "while i < len(word):\n",
    "    letter = word[i]\n",
    "\n",
    "    i += 1\n",
    "\n",
    "    if letter == 't':\n",
    "        pass # do nothing\n",
    "    \n",
    "    print(letter, end = \" \")\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Comprehension"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['k', 'j', 's', 'l', 'k', 'f', 'j', 'a', 'l', 'k', 'f']"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "letters = [char for char in \"kjslkfjalkf\"]\n",
    "letters"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 2, 4, 6, 8]"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "evens = [num for num in range(0, 10) if num % 2 == 0]\n",
    "evens"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'n': 110, 'a': 97, 'm': 109, 'e': 101}"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "name_order = {char : ord(char) for char in \"name\"}\n",
    "name_order"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "97"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "name_order['a']"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n",
      "[None, None, None, None, None, None, None, None, None, None]\n"
     ]
    }
   ],
   "source": [
    "matrix = [[None for i in range(10)] for i in range(10)]\n",
    "for row in matrix:\n",
    "    print(row)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Generators"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 5, 10]"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def factors1(n):\n",
    "    results = []\n",
    "\n",
    "    for k in range(1, n + 1):\n",
    "        if n % k == 0:  # divides evenly, thus k is a factor\n",
    "            results.append(k)  # add k to the list of factors\n",
    "    \n",
    "    return results\n",
    "\n",
    "factors1(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<generator object factors2 at 0x7f7fad3f54d0>"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def factors2(n):\n",
    "\n",
    "    for k in range(1, n + 1):\n",
    "        if n % k == 0:\n",
    "            yield k  # return k as an individual item and continue\n",
    "\n",
    "factors2(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 5, 10]"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "list(factors2(10)) # converted to list"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "- **iteration** => 5 lines of code\n",
    "- **generator using yield** => 3 lines of code"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Iterators"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "h e l l o "
     ]
    }
   ],
   "source": [
    "word = list(\"hello\")\n",
    "for i in word:\n",
    "    print(i, end = \" \")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "e l l o "
     ]
    }
   ],
   "source": [
    "# if I want to start at second index?\n",
    "word = iter(word)\n",
    "\n",
    "next(word)\n",
    "\n",
    "for i in word:\n",
    "    print(i, end = \" \")"
   ]
  }
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