|
| 1 | +{ |
| 2 | + "cells": [ |
| 3 | + { |
| 4 | + "cell_type": "markdown", |
| 5 | + "metadata": {}, |
| 6 | + "source": [ |
| 7 | + "# map()\n", |
| 8 | + "Map applies a function to all the items in an input_list. Here is the \n", |
| 9 | + "blueprint:\n", |
| 10 | + "\n", |
| 11 | + "```python\n", |
| 12 | + "map(function_to_apply, list_of_inputs)\n", |
| 13 | + "```" |
| 14 | + ] |
| 15 | + }, |
| 16 | + { |
| 17 | + "cell_type": "markdown", |
| 18 | + "metadata": {}, |
| 19 | + "source": [ |
| 20 | + "Most of the times we want to pass all the list elements to a function \n", |
| 21 | + "one-by-one and then collect the output. For instance:" |
| 22 | + ] |
| 23 | + }, |
| 24 | + { |
| 25 | + "cell_type": "code", |
| 26 | + "execution_count": 11, |
| 27 | + "metadata": {}, |
| 28 | + "outputs": [ |
| 29 | + { |
| 30 | + "name": "stdout", |
| 31 | + "output_type": "stream", |
| 32 | + "text": [ |
| 33 | + "[1, 2, 3, 4, 5]\n", |
| 34 | + "[1, 4, 9, 16, 25]\n" |
| 35 | + ] |
| 36 | + } |
| 37 | + ], |
| 38 | + "source": [ |
| 39 | + "items = [1, 2, 3, 4, 5]\n", |
| 40 | + "squared_items = []\n", |
| 41 | + "for i in items:\n", |
| 42 | + " squared_items.append(i**2)\n", |
| 43 | + " \n", |
| 44 | + "print(items)\n", |
| 45 | + "print(squared_items)" |
| 46 | + ] |
| 47 | + }, |
| 48 | + { |
| 49 | + "cell_type": "markdown", |
| 50 | + "metadata": {}, |
| 51 | + "source": [ |
| 52 | + "Map allows us to implement this in a much simpler and nicer way. Here you go:" |
| 53 | + ] |
| 54 | + }, |
| 55 | + { |
| 56 | + "cell_type": "code", |
| 57 | + "execution_count": 12, |
| 58 | + "metadata": {}, |
| 59 | + "outputs": [ |
| 60 | + { |
| 61 | + "name": "stdout", |
| 62 | + "output_type": "stream", |
| 63 | + "text": [ |
| 64 | + "[1, 2, 3, 4, 5]\n", |
| 65 | + "[1, 4, 9, 16, 25]\n" |
| 66 | + ] |
| 67 | + } |
| 68 | + ], |
| 69 | + "source": [ |
| 70 | + "def square(x):\n", |
| 71 | + " return x**2\n", |
| 72 | + "\n", |
| 73 | + "items = [1, 2, 3, 4, 5]\n", |
| 74 | + "squared_items = list(map(square, items))\n", |
| 75 | + "\n", |
| 76 | + "print(items)\n", |
| 77 | + "print(squared_items)" |
| 78 | + ] |
| 79 | + }, |
| 80 | + { |
| 81 | + "cell_type": "markdown", |
| 82 | + "metadata": {}, |
| 83 | + "source": [ |
| 84 | + "Most of the times we use lambdas with `map`, so I did the same. " |
| 85 | + ] |
| 86 | + }, |
| 87 | + { |
| 88 | + "cell_type": "code", |
| 89 | + "execution_count": 13, |
| 90 | + "metadata": {}, |
| 91 | + "outputs": [ |
| 92 | + { |
| 93 | + "name": "stdout", |
| 94 | + "output_type": "stream", |
| 95 | + "text": [ |
| 96 | + "[1, 2, 3, 4, 5]\n", |
| 97 | + "[1, 4, 9, 16, 25]\n" |
| 98 | + ] |
| 99 | + } |
| 100 | + ], |
| 101 | + "source": [ |
| 102 | + "items = [1, 2, 3, 4, 5]\n", |
| 103 | + "squared = list(map(lambda x: x**2, items))\n", |
| 104 | + "\n", |
| 105 | + "print(items)\n", |
| 106 | + "print(squared)" |
| 107 | + ] |
| 108 | + }, |
| 109 | + { |
| 110 | + "cell_type": "markdown", |
| 111 | + "metadata": {}, |
| 112 | + "source": [ |
| 113 | + "Instead of a list of inputs, we can even apply a list of functions!" |
| 114 | + ] |
| 115 | + }, |
| 116 | + { |
| 117 | + "cell_type": "code", |
| 118 | + "execution_count": 16, |
| 119 | + "metadata": {}, |
| 120 | + "outputs": [ |
| 121 | + { |
| 122 | + "name": "stdout", |
| 123 | + "output_type": "stream", |
| 124 | + "text": [ |
| 125 | + "[0, 0]\n", |
| 126 | + "[1, 2]\n", |
| 127 | + "[4, 4]\n", |
| 128 | + "[9, 6]\n", |
| 129 | + "[16, 8]\n" |
| 130 | + ] |
| 131 | + } |
| 132 | + ], |
| 133 | + "source": [ |
| 134 | + "def square(x):\n", |
| 135 | + "\treturn (x*x)\n", |
| 136 | + "def double(x):\n", |
| 137 | + "\treturn (2*x)\n", |
| 138 | + "\n", |
| 139 | + "# For the numbers from 0 to 4, square it and double it\n", |
| 140 | + "funcs = [square, double]\n", |
| 141 | + "for i in range(5):\n", |
| 142 | + " # value will be a list containing two elements [i^2, 2*i], one for each function in funcs\n", |
| 143 | + " value = list(map(lambda x: x(i), funcs))\n", |
| 144 | + " print(value)" |
| 145 | + ] |
| 146 | + }, |
| 147 | + { |
| 148 | + "cell_type": "code", |
| 149 | + "execution_count": null, |
| 150 | + "metadata": {}, |
| 151 | + "outputs": [], |
| 152 | + "source": [] |
| 153 | + } |
| 154 | + ], |
| 155 | + "metadata": { |
| 156 | + "kernelspec": { |
| 157 | + "display_name": "Python 3", |
| 158 | + "language": "python", |
| 159 | + "name": "python3" |
| 160 | + }, |
| 161 | + "language_info": { |
| 162 | + "codemirror_mode": { |
| 163 | + "name": "ipython", |
| 164 | + "version": 3 |
| 165 | + }, |
| 166 | + "file_extension": ".py", |
| 167 | + "mimetype": "text/x-python", |
| 168 | + "name": "python", |
| 169 | + "nbconvert_exporter": "python", |
| 170 | + "pygments_lexer": "ipython3", |
| 171 | + "version": "3.6.4" |
| 172 | + } |
| 173 | + }, |
| 174 | + "nbformat": 4, |
| 175 | + "nbformat_minor": 2 |
| 176 | +} |
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