1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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2 % Tutorial slides on Python. |
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3 % |
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4 % Author: Prabhu Ramachandran <prabhu at aero.iitb.ac.in> |
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5 % Copyright (c) 2005-2008, Prabhu Ramachandran |
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6 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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7 |
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8 \documentclass[14pt,compress]{beamer} |
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9 %\documentclass[draft]{beamer} |
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10 %\documentclass[compress,handout]{beamer} |
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11 %\usepackage{pgfpages} |
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12 %\pgfpagesuselayout{2 on 1}[a4paper,border shrink=5mm] |
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13 |
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14 % Modified from: generic-ornate-15min-45min.de.tex |
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15 \mode<presentation> |
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16 { |
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17 \usetheme{Warsaw} |
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18 \useoutertheme{split} |
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19 \setbeamercovered{transparent} |
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20 } |
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21 |
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22 \usepackage[english]{babel} |
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23 \usepackage[latin1]{inputenc} |
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24 %\usepackage{times} |
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25 \usepackage[T1]{fontenc} |
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26 |
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27 % Taken from Fernando's slides. |
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28 \usepackage{ae,aecompl} |
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29 \usepackage{mathpazo,courier,euler} |
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30 \usepackage[scaled=.95]{helvet} |
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31 |
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32 \definecolor{darkgreen}{rgb}{0,0.5,0} |
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33 |
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34 \usepackage{listings} |
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35 \lstset{language=Python, |
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36 basicstyle=\ttfamily, |
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37 commentstyle=\color{red}\itshape, |
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38 stringstyle=\color{darkgreen}, |
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39 showstringspaces=false, |
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40 keywordstyle=\color{blue}\bfseries} |
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41 |
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42 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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43 % Macros |
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44 \setbeamercolor{emphbar}{bg=blue!20, fg=black} |
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45 \newcommand{\emphbar}[1] |
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46 {\begin{beamercolorbox}[rounded=true]{emphbar} |
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47 {#1} |
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48 \end{beamercolorbox} |
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49 } |
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50 \newcounter{time} |
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51 \setcounter{time}{0} |
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52 \newcommand{\inctime}[1]{\addtocounter{time}{#1}{\tiny \thetime\ m}} |
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53 |
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54 \newcommand{\typ}[1]{\texttt{#1}} |
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55 |
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56 \newcommand{\kwrd}[1]{ \texttt{\textbf{\color{blue}{#1}}} } |
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57 |
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58 %%% This is from Fernando's setup. |
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59 % \usepackage{color} |
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60 % \definecolor{orange}{cmyk}{0,0.4,0.8,0.2} |
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61 % % Use and configure listings package for nicely formatted code |
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62 % \usepackage{listings} |
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63 % \lstset{ |
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64 % language=Python, |
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65 % basicstyle=\small\ttfamily, |
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66 % commentstyle=\ttfamily\color{blue}, |
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67 % stringstyle=\ttfamily\color{orange}, |
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68 % showstringspaces=false, |
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69 % breaklines=true, |
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70 % postbreak = \space\dots |
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71 % } |
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72 |
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73 |
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74 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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75 % Title page |
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76 \title[Basic Python]{Python:\\A great programming toolkit} |
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77 |
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78 \author[FOSSEE Team] {Asokan Pichai\\Prabhu Ramachandran} |
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79 |
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80 \institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay} |
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81 \date[] {10, October 2009} |
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82 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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83 |
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84 %\pgfdeclareimage[height=0.75cm]{iitmlogo}{iitmlogo} |
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85 %\logo{\pgfuseimage{iitmlogo}} |
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86 |
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87 |
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88 %% Delete this, if you do not want the table of contents to pop up at |
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89 %% the beginning of each subsection: |
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90 \AtBeginSubsection[] |
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91 { |
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92 \begin{frame}<beamer> |
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93 \frametitle{Outline} |
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94 \tableofcontents[currentsection,currentsubsection] |
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95 \end{frame} |
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96 } |
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97 |
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98 |
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99 % If you wish to uncover everything in a step-wise fashion, uncomment |
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100 % the following command: |
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101 %\beamerdefaultoverlayspecification{<+->} |
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102 |
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103 %\includeonlyframes{current,current1,current2,current3,current4,current5,current6} |
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104 |
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105 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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106 % DOCUMENT STARTS |
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107 \begin{document} |
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108 |
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109 \begin{frame} |
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110 \titlepage |
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111 \end{frame} |
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112 \begin{frame} |
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113 {Acknowledgements} |
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114 \begin{center} |
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115 This program is conducted by\\ |
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116 IIT, Bombay\\ |
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117 through CDEEP\\as part of the open source initiatives\\ |
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118 under the aegis of\\ |
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119 \alert{National Mission on Education through ICT,} \\ |
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120 Ministry of HRD. |
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121 \end{center} |
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122 \end{frame} |
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123 |
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124 \begin{frame} |
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125 \frametitle{Outline} |
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126 \tableofcontents |
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127 % You might wish to add the option [pausesections] |
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128 \end{frame} |
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129 |
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130 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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131 % TODO |
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132 % |
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133 % * Add slide on Python packages (modules) |
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134 % * Add slides on reference counting. |
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135 |
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136 \section{Agenda} |
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137 \begin{frame}{About the Workshop} |
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138 \begin{description} |
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139 \item[Day 1, Session 1] Sat 09:30--11:00 |
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140 \item[Day 1, Session 2] Sat 11:15--12:45 |
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141 \item[Day 1, Session 3] Sat 13:45--15:15 |
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142 \item[Day 1, Session 4] Sat 15:30--17:00 |
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143 \item[Day 2, Session 1] Sun 09:30--11:00 |
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144 \item[Day 2, Session 2] Sun 11:15--12:45 |
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145 \item[Day 2, Session 3] Sun 13:45--15:15 |
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146 \item[Day 2, Session 4] Sun 15:30--17:00 |
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147 \end{description} |
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148 \end{frame} |
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149 |
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150 \section{Agenda} |
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151 \begin{frame}{About the Workshop} |
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152 \begin{block}{Goal of the workshop} |
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153 Successful participants will be able to use python as their scripting and problem solving language. |
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154 \end{block} |
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155 \begin{block}{Workshop Audience} |
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156 Aimed at Engg., Mathematics and Science teachers but should serve a similar purpose for others. |
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157 \end{block} |
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158 \begin{block}{Focus of the workshop} |
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159 Focus on basic numerics and plotting |
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160 \end{block} |
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161 \end{frame} |
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162 |
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163 \begin{frame}{Checklist} |
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164 \begin{block}{python} |
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165 Type python at the command line. Do you see version 2.5 or later? |
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166 \end{block} |
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167 \begin{block}{IPython} |
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168 Is IPython available? |
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169 \end{block} |
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170 \begin{block}{Editor} |
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171 Which editor? scite, vim, emacs, \ldots |
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172 \end{block} |
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173 \end{frame} |
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174 |
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175 \section{Overview} |
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176 \begin{frame}{Session 1} |
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177 \begin{itemize} |
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178 \item Introduction and motivation |
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179 \item Using the interpreter(s) |
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180 \item Basic data types: int, float, string |
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181 \item Basic data structures: list |
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182 \item Basic console IO: \texttt{raw\_input(), print} |
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183 \item Basic control flow: \texttt{if, while} |
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184 \item Problem set 1 |
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185 \item Functions $\rightarrow$ Problem set 2 |
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186 \item lists, \texttt{for} $\rightarrow$ Problem set 3 |
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187 \item IO, Modules $\rightarrow$ Problem sets 4,5, \ldots |
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188 \end{itemize} |
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189 \end{frame} |
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190 |
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191 \begin{frame} |
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192 \frametitle{Introduction} |
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193 \begin{itemize} |
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194 \item Creator and BDFL: Guido van Rossum |
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195 \item December 1989 |
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196 \item ``Python'' as in Monty Python's Flying Circus |
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197 \item 2.6.x |
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198 \item PSF license (like BSD: no strings attached) |
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199 \item Highly cross platform |
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200 \item Nokia series 60! |
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201 \item \alert{Philosophy:} Simple and complete by design |
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202 \end{itemize} |
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203 \end{frame} |
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204 |
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205 \begin{frame} |
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206 \frametitle{Resources} |
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207 \begin{itemize} |
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208 \item Part of many GNU/Linux distributions |
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209 \item Web: \url{http://www.python.org} |
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210 \item Doc: \url{http://www.python.org/doc} |
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211 \item Free Tutorials: |
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212 \begin{itemize} |
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213 \item Official Python tutorial: \url{http://docs.python.org/tut/tut.html} |
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214 \item Byte of Python: \url{http://www.byteofpython.info/} |
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215 \item Dive into Python: \url{http://diveintopython.org/} |
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216 \end{itemize} |
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217 \end{itemize} |
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218 \end{frame} |
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219 |
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220 \begin{frame} |
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221 \frametitle{Why Python?} |
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222 \begin{itemize} |
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223 \item Readable and easy to use |
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224 \item High level, interpreted, modular, OO |
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225 \item Much faster development cycle |
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226 \item Powerful interactive environment |
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227 \item Rapid application development |
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228 \item Rich standard library and modules |
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229 \item Interfaces well with C++, C and FORTRAN |
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230 \item \alert{More than a math package $\Rightarrow$ some extra work compared to math packages} |
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231 \end{itemize} |
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232 \end{frame} |
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233 |
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234 \begin{frame} |
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235 \frametitle{Use cases} |
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236 \begin{itemize} |
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237 \item NASA: Space Shuttle Mission Design |
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238 \item AstraZeneca: Collaborative Drug Discovery |
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239 \item ForecastWatch.com: Helps Meteorologists |
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240 \item Industrial Light \& Magic: Runs on Python |
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241 \item Zope: Commercial grade Toolkit |
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242 \item Plone: Professional high feature CMS |
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243 \item RedHat: install scripts, sys-admin tools |
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244 \item Django: A great web application framework |
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245 \item Google: A strong python shop |
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246 \end{itemize} |
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247 \end{frame} |
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248 |
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249 \begin{frame} |
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250 \frametitle{To sum up, python is\ldots} |
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251 \begin{itemize} |
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252 \item dynamically typed, interpreted $\rightarrow$ rapid testing/prototyping |
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253 \item powerful, very high level |
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254 \item has full introspection |
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255 \item Did we mention powerful? |
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256 \end{itemize} |
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257 \begin{block}{But \ldots} |
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258 may be wanting in performance. specialised resources such as SWIG, \alert{Cython} are available |
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259 \end{block} |
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260 \inctime{15} |
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261 \end{frame} |
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262 |
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263 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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264 % TIME: 10 m, running 10m |
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265 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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266 |
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267 \section{Python} |
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268 |
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269 \subsection{Getting Started} |
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270 |
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271 \begin{frame}[fragile]{At the prompt, type the following} |
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272 \begin{lstlisting} |
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273 >>> print 'Hello Python' |
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274 >>> print 3124 * 126789 |
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275 >>> 1786 % 12 |
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276 >>> 3124 * 126789 |
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277 >>> a = 3124 * 126789 |
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278 >>> big = 12345678901234567890 ** 3 |
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279 >>> verybig = big * big * big * big |
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280 >>> 12345**6, 12345**67, 12345**678 |
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281 \end{lstlisting} |
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282 \end{frame} |
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283 |
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284 \begin{frame}[fragile]{At the prompt, type the following} |
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285 \begin{lstlisting} |
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286 >>> s = 'Hello ' |
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287 >>> p = 'World' |
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288 >>> s + p |
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289 >>> s * 12 |
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290 >>> s * s |
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291 >>> s + p * 12, (s + p)* 12 |
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292 >>> s * 12 + p * 12 |
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293 >>> 12 * s |
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294 \end{lstlisting} |
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295 \end{frame} |
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296 |
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297 \begin{frame}[fragile]{At the prompt, type the following} |
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298 \begin{lstlisting} |
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299 >>> 17/2 |
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300 >>> 17/2.0 |
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301 >>> 17.0/2 |
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302 >>> 17.0/8.5 |
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303 >>> int(17/2.0) |
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304 >>> float(17/2) |
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305 >>> str(17/2.0) |
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306 >>> round( 7.5 ) |
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307 \end{lstlisting} |
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308 \begin{block}{Mini exercise} |
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309 Round a float to the nearest integer, using \texttt{int()}? |
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310 \end{block} |
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311 \end{frame} |
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312 |
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313 \begin{frame}{Midi exercises} |
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314 \begin{center} |
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315 \begin{itemize} |
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316 \item What does this do? |
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317 \item \texttt{round(amount * 10) /10.0 } |
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318 \end{itemize} |
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319 \end{center} |
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320 \end{frame} |
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321 |
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322 \begin{frame}{More exercises?} |
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323 \begin{center} |
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324 \begin{block}{Round sums} |
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325 How to round a number to the nearest 5 paise?\\ |
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326 \begin{description} |
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327 \item[Remember] 17.23 $\rightarrow$ 17.25,\\ while 17.22 $\rightarrow$ 17.20\\ |
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328 \end{description} |
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329 How to round a number to the nearest 20 paise? |
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330 \end{block} |
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331 \end{center} |
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332 \end{frame} |
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333 |
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334 \begin{frame}[fragile] {A question of good style} |
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335 \begin{lstlisting} |
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336 amount = 12.68 |
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337 denom = 0.05 |
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338 nCoins = round(amount/denom) |
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339 rAmount = nCoins * denom |
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340 \end{lstlisting} |
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341 \pause |
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342 \begin{block}{Style Rule \#1} |
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343 Naming is 80\% of programming |
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344 \end{block} |
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345 \end{frame} |
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346 |
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347 |
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348 \begin{frame}[fragile] |
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349 \frametitle{Odds and ends} |
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350 \begin{itemize} |
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351 \item Case sensitive |
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352 \item Dynamically typed $\Rightarrow$ need not specify a type |
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353 \begin{lstlisting} |
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354 a = 1 |
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355 a = 1.1 |
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356 a = "Now I am a string!" |
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357 \end{lstlisting} |
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358 \item Comments: |
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359 \begin{lstlisting} |
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360 a = 1 # In-line comments |
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361 # Comment in a line to itself. |
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362 a = "# This is not a comment!" |
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363 \end{lstlisting} |
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364 \end{itemize} |
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365 \inctime{15} |
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366 \end{frame} |
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367 |
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368 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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369 % TIME: 10 m, running 20m |
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370 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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371 |
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372 \subsection{Data types} |
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373 \begin{frame} |
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374 \frametitle{Basic types} |
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375 \begin{itemize} |
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376 \item Numbers: float, int, long, complex |
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377 \item Strings |
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378 \item Boolean |
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379 \end{itemize} |
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380 \begin{block}{Also to be discussed later} |
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381 tuples, lists, dictionaries, functions, objects\ldots |
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382 \end{block} |
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383 \end{frame} |
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384 |
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385 \begin{frame}[fragile] |
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386 \frametitle{Numbers} |
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387 \vspace*{-0.25in} |
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388 \begin{lstlisting} |
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389 >>> a = 1 # Int. |
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390 >>> l = 1000000L # Long |
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391 >>> e = 1.01325e5 # float |
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392 >>> f = 3.14159 # float |
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393 >>> c = 1+1j # Complex! |
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394 >>> print f*c/a |
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395 (3.14159+3.14159j) |
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396 >>> print c.real, c.imag |
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397 1.0 1.0 |
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398 >>> abs(c) |
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399 1.4142135623730951 |
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400 >>> abs( 8 - 9.5 ) |
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401 1.5 |
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402 \end{lstlisting} |
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403 \end{frame} |
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404 |
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405 \begin{frame}[fragile] |
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406 \frametitle{Boolean} |
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407 \begin{lstlisting} |
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408 >>> t = True |
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409 >>> f = not t |
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410 False |
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411 >>> f or t |
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412 True |
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413 >>> f and t |
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414 False |
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415 \end{lstlisting} |
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416 \begin{block}{Try:} |
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417 NOT True\\ |
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418 not TRUE |
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419 \end{block} |
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420 \end{frame} |
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421 |
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422 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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423 % TIME: 10 m, running 30m |
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424 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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425 |
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426 \begin{frame}[fragile] |
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427 \frametitle{Relational and logical operators} |
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428 \begin{lstlisting} |
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429 >>> a, b, c = -1, 0, 1 |
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430 >>> a == b |
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431 False |
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432 >>> a <= b |
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433 True |
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434 >>> a + b != c |
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435 True |
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436 >>> a < b < c |
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437 True |
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438 >>> c >= a + b |
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439 True |
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440 \end{lstlisting} |
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441 \end{frame} |
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442 |
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443 \begin{frame}[fragile] |
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444 \frametitle{Strings} |
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445 \begin{lstlisting} |
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446 s = 'this is a string' |
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447 s = 'This one has "quotes" inside!' |
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448 s = "I have 'single-quotes' inside!" |
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449 l = "A string spanning many lines\ |
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450 one more line\ |
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451 yet another" |
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452 t = """A triple quoted string does |
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453 not need to be escaped at the end and |
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454 "can have nested quotes" etc.""" |
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455 \end{lstlisting} |
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456 \end{frame} |
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457 |
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458 \begin{frame}[fragile] |
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459 \frametitle{More Strings} |
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460 \vspace*{-0.2in} |
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461 \begin{lstlisting} |
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462 >>> w = "hello" |
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463 >>> print w[0] + w[2] + w[-1] |
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464 hlo |
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465 >>> len(w) # guess what |
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466 5 |
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467 >>> s = u'Unicode strings!' |
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468 >>> # Raw strings (note the leading 'r') |
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469 ... r_s = r'A string $\alpha \nu$' |
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470 \end{lstlisting} |
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471 \pause |
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472 \begin{lstlisting} |
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473 >>> w[0] = 'H' # Can't do that! |
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474 Traceback (most recent call last): |
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475 File "<stdin>", line 1, in ? |
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476 TypeError: object does not support item assignment |
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477 \end{lstlisting} |
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478 \end{frame} |
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479 |
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480 \begin{frame} |
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481 \frametitle{Let us switch to IPython} |
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482 Why? |
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483 \begin{block} |
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484 {Better help (and a lot more)} |
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485 Tab completion\\ |
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486 ?\\ |
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487 .?\\ |
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488 object.function? |
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489 \end{block} |
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490 \end{frame} |
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491 |
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492 \begin{frame}[fragile] |
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493 \frametitle{More on strings} |
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494 \begin{lstlisting} |
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495 In [1]: a = 'hello world' |
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496 In [2]: a.startswith('hell') |
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497 Out[2]: True |
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498 In [3]: a.endswith('ld') |
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499 Out[3]: True |
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500 In [4]: a.upper() |
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501 Out[4]: 'HELLO WORLD' |
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502 In [5]: a.upper().lower() |
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503 Out[5]: 'hello world' |
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504 \end{lstlisting} |
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505 \end{frame} |
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506 |
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507 \begin{frame}[fragile]{Still with strings} |
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508 \begin{lstlisting} |
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509 In [6]: a.split() |
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510 Out[6]: ['hello', 'world'] |
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511 In [7]: ''.join(['a', 'b', 'c']) |
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512 Out[7]: 'abc' |
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513 In [8] 'd' in ''.join( 'a', 'b', 'c') |
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514 Out[8]: False |
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515 \end{lstlisting} |
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516 \begin{block}{Try:} |
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517 \texttt{a.split( 'o' )}\\ |
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518 \texttt{'x'.join( a.split( 'o' ) )} |
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519 \end{block} |
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520 \end{frame} |
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521 |
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522 \begin{frame}[fragile]{Surprise! strings!!} |
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523 \begin{lstlisting} |
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524 In [11]: x, y = 1, 1.2 |
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525 In [12]: 'x is %s, y is %s' %(x, y) |
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526 Out[12]: 'x is 1, y is 1.234' |
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527 \end{lstlisting} |
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528 \begin{block}{Try:} |
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529 \texttt{'x is \%d, y is \%f' \%(x, y) }\\ |
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530 \texttt{'x is \%3d, y is \%4.2f' \%(x, y) } |
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531 \end{block} |
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532 \small |
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533 \url{docs.python.org/lib/typesseq-strings.html}\\ |
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534 \end{frame} |
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535 |
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536 \begin{frame} |
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537 {Interlude} |
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538 \begin{block} |
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539 {A classic problem} |
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540 How to interchange values of two variables? Please note that the type of either variable is unknown and it is not necessary that both be of the same type even! |
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541 \end{block} |
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542 \inctime{30} |
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543 \end{frame} |
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544 |
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545 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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546 % TIME: 25 m+ Interlude break 5 mins, running 60m |
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547 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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548 |
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549 \subsection{Control flow} |
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550 \begin{frame} |
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551 \frametitle{Control flow constructs} |
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552 \begin{itemize} |
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553 \item \kwrd{if/elif/else}: branching |
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554 \item \kwrd{while}: looping |
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555 \item \kwrd{for}: iterating |
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556 \item \kwrd{break, continue}: modify loop |
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557 \item \kwrd{pass}: syntactic filler |
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558 \end{itemize} |
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559 \end{frame} |
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560 |
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561 \begin{frame}[fragile] |
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562 \frametitle{Basic conditional flow} |
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563 \begin{lstlisting} |
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564 In [21]: a = 7 |
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565 In [22]: b = 8 |
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566 In [23]: if a > b: |
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567 ....: print 'Hello' |
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568 ....: else: |
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569 ....: print 'World' |
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570 ....: |
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571 ....: |
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572 World |
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573 \end{lstlisting} |
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574 Let us switch to creating a file |
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575 \end{frame} |
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576 |
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577 \begin{frame} |
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578 {Creating python files} |
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579 \begin{itemize} |
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580 \item aka scripts |
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581 \item use your editor |
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582 \item Note that white space is the way to specify blocks! |
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583 \item extension \typ{.py} |
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584 \item run with \texttt{python hello.py} at the command line |
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585 \item in IPython\ldots |
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586 \end{itemize} |
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587 \end{frame} |
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588 |
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589 \begin{frame}[fragile] |
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590 \frametitle{\typ{If...elif...else} example} |
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591 \begin{lstlisting} |
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592 x = int(raw_input("Enter an integer:")) |
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593 if x < 0: |
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594 print 'Be positive!' |
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595 elif x == 0: |
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596 print 'Zero' |
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597 elif x == 1: |
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598 print 'Single' |
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599 else: |
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600 print 'More' |
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601 \end{lstlisting} |
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602 \end{frame} |
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603 |
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604 \begin{frame}{Simple IO} |
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605 \begin{block} |
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606 {Console Input} |
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607 \texttt{raw\_input()} waits for user input.\\Prompt string is optional.\\ |
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608 All keystrokes are Strings!\\\texttt{int()} converts string to int. |
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609 \end{block} |
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610 \begin{block} |
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611 {Console output} |
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612 \texttt{print} is straight forward. Major point to remember is the distinction between \texttt{print x} and \texttt{print x,} |
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613 \end{block} |
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614 \end{frame} |
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615 |
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616 \begin{frame}[fragile] |
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617 \frametitle{Basic looping} |
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618 \begin{lstlisting} |
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619 # Fibonacci series: |
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620 # the sum of two elements |
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621 # defines the next |
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622 a, b = 0, 1 |
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623 while b < 10: |
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624 print b, |
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625 a, b = b, a + b |
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626 |
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627 \end{lstlisting} |
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628 \typ{1 1 2 3 5 8}\\ |
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629 \alert{Recall it is easy to write infinite loops with \kwrd{while}} |
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630 \inctime{20} |
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631 \end{frame} |
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632 |
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633 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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634 % TIME: 20 m, running 80m |
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635 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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636 \end{document} |
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