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    21 \usepackage{listings}

    22 \lstset{language=Python, basicstyle=\ttfamily\bfseries,

    23 commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},

    24 showstringspaces=false, keywordstyle=\color{blue}\bfseries}

    25 \providecommand{\alert}[1]{\textbf{#1}}

    26 

    27 \title{Getting started with arrays}

    28 \author{FOSSEE}

    29 \date{}

    30 

    31 \usetheme{Warsaw}\usecolortheme{default}\useoutertheme{infolines}\setbeamercovered{transparent}

    32 \begin{document}

    33 

    34 \maketitle

    35 

    36 

    37 

    38 

    39 

    40 

    41 

    42 

    43 

    44 \begin{frame}

    45 \frametitle{Outline}

    46 \label{sec-1}

    47 

    48 \begin{itemize}

    49 \item Arrays

    50 

    51 \begin{itemize}

    52 \item why arrays over lists

    53 \end{itemize}

    54 

    55 \item Creating arrays

    56 \item Array operations

    57 \end{itemize}

    58 \end{frame}

    59 \begin{frame}

    60 \frametitle{Overview of Arrays}

    61 \label{sec-2}

    62 

    63 \begin{itemize}

    64 \item Arrays are homogeneous data structures.

    65 

    66 \begin{itemize}

    67 \item elements have to the same data type

    68 \end{itemize}

    69 

    70 \item Arrays are faster compared to lists

    71 

    72 \begin{itemize}

    73 \item at least \emph{80-100 times} faster than lists

    74 \end{itemize}

    75 

    76 \end{itemize}

    77 \end{frame}

    78 \begin{frame}[fragile]

    79 \frametitle{Creating Arrays}

    80 \label{sec-3}

    81 

    82 \begin{itemize}

    83 \item Creating a 1-dimensional array

    84 \end{itemize}

    85 

    86 \begin{verbatim}

    87    In []: a1 = array([1, 2, 3, 4])

    88 \end{verbatim}

    89 

    90 \begin{itemize}

    91 \item Creating a 2-dimensional array

    92 \end{itemize}

    93 

    94 \begin{verbatim}

    95    In []: a2 = array([[1,2,3,4],[5,6,7,8]])

    96 \end{verbatim}

    97 

    98 \begin{itemize}

    99 \item Easier method of creating array with consecutive elements.

   100 \end{itemize}

   101 

   102 \begin{verbatim}

   103    In []: ar = arange(1,9)

   104 \end{verbatim}

   105 \end{frame}

   106 \begin{frame}[fragile]

   107 \frametitle{\texttt{reshape()} method}

   108 \label{sec-4}

   109 

   110 \begin{itemize}

   111 \item To reshape an array

   112 \end{itemize}

   113 

   114 \begin{verbatim}

   115    In []: ar.reshape(2, 4)

   116    In []: ar.reshape(4, 2)

   117    In []: ar = ar.reshape(2, 4)

   118 \end{verbatim}

   119 \end{frame}

   120 \begin{frame}[fragile]

   121 \frametitle{Creating \texttt{array} from \texttt{list}.}

   122 \label{sec-5}

   123 

   124 \begin{itemize}

   125 \item \texttt{array()} method accepts list as argument

   126 \item Creating a list

   127 \begin{verbatim}

   128     In []: l1 = [1, 2, 3, 4]

   129 \end{verbatim}

   130 

   131 \item Creating an array

   132 \begin{verbatim}

   133      In []: a3 = array(l1)

   134 \end{verbatim}

   135 

   136 \end{itemize}

   137 \end{frame}

   138 \begin{frame}

   139 \frametitle{Exercise 1}

   140 \label{sec-6}

   141 

   142   Create a 3-dimensional array of the order (2, 2, 4).

   143 \end{frame}

   144 \begin{frame}[fragile]

   145 \frametitle{\texttt{.shape} of array}

   146 \label{sec-7}

   147 

   148 \begin{itemize}

   149 \item \texttt{.shape}

   150     To find the shape of the array

   151 \begin{verbatim}

   152      In []: a1.shape

   153 \end{verbatim}

   154 

   155 \item \texttt{.shape}

   156     returns a tuple of shape

   157 \end{itemize}

   158 \end{frame}

   159 \begin{frame}

   160 \frametitle{Exercise 2}

   161 \label{sec-8}

   162 

   163   Find out the shape of the other arrays(a2, a3, ar) that we have created.

   164 \end{frame}

   165 \begin{frame}[fragile]

   166 \frametitle{Homogeneous data}

   167 \label{sec-9}

   168 

   169 \begin{itemize}

   170 \item All elements in array should be of same type

   171 \begin{verbatim}

   172      In []: a4 = array([1,2,3,'a string'])

   173 \end{verbatim}

   174 

   175 \end{itemize}

   176 \end{frame}

   177 \begin{frame}[fragile]

   178 \frametitle{Implicit type casting}

   179 \label{sec-10}

   180 

   181 \begin{verbatim}

   182     In []: a4

   183 \end{verbatim}

   184 

   185     All elements are type casted to string type

   186 \end{frame}

   187 \begin{frame}

   188 \frametitle{\texttt{identity()}, \texttt{zeros()} methods}

   189 \label{sec-11}

   190 

   191 \begin{itemize}

   192 \item \texttt{identity(n)}

   193     Creates an identity matrix, a square matrix of order (n, n) with diagonal elements 1 and others 0.

   194 \item \texttt{zeros((m, n))}

   195     Creates an \texttt{m X n} matrix with all elements 0.

   196 \end{itemize}

   197 \end{frame}

   198 \begin{frame}

   199 \frametitle{Learning exercise}

   200 \label{sec-12}

   201 

   202 \begin{itemize}

   203 \item Find out about

   204 

   205 \begin{itemize}

   206 \item \texttt{zeros\_like()}

   207 \item \texttt{ones()}

   208 \item \texttt{ones\_like()}

   209 \end{itemize}

   210 

   211 \end{itemize}

   212 \end{frame}

   213 \begin{frame}

   214 \frametitle{Array operations}

   215 \label{sec-13}

   216 

   217 \begin{itemize}

   218 \item \texttt{a1 * 2}

   219     returns a new array with all elements of \texttt{a1} multiplied by \texttt{2}.

   220 

   221 \begin{itemize}

   222 \item Similarly \texttt{+}, \texttt{-} \& \texttt{/}.

   223 \end{itemize}

   224 

   225 \item \texttt{a1 + 2}

   226     returns a new array with all elements of \texttt{a1} summed with \texttt{2}.

   227 \item \texttt{a1 += 2}

   228     adds \texttt{2} to all elements of array \texttt{a1}.

   229 

   230 \begin{itemize}

   231 \item Similarly \texttt{-=}, \texttt{*=} \& \texttt{/=}.

   232 \end{itemize}

   233 

   234 \item \texttt{a1 + a2}

   235     does elements-wise addition.

   236 

   237 \begin{itemize}

   238 \item Similarly \texttt{-}, \texttt{*} \& \texttt{/}.

   239 \end{itemize}

   240 

   241 \item \texttt{a1 * a2}

   242     does element-wise multiplication

   243 \end{itemize}

   244 

   245 

   246   \textbf{Note} - array(A) * array(B) does element wise multiplication and not matrix multiplication

   247 \end{frame}

   248 \begin{frame}

   249 \frametitle{Summary}

   250 \label{sec-14}

   251 

   252   In this tutorial we covered,

   253 \begin{itemize}

   254 \item Basics of arrays

   255 \item Creating arrays

   256 \item Arrays from lists

   257 \item Basic array operations

   258 \end{itemize}

   259 \end{frame}

   260 \begin{frame}

   261 \frametitle{Thank you!}

   262 \label{sec-15}

   263 

   264   \begin{block}{}

   265   \begin{center}

   266   This spoken tutorial has been produced by the

   267   \textcolor{blue}{FOSSEE} team, which is funded by the 

   268   \end{center}

   269   \begin{center}

   270     \textcolor{blue}{National Mission on Education through \\

   271       Information \& Communication Technology \\ 

   272       MHRD, Govt. of India}.

   273   \end{center}  

   274   \end{block}

   275 \end{frame}

   276 

   277 \end{document}