% Created 2010-10-11 Mon 23:02

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

\title{Dictionaries}

\author{FOSSEE}

\date{}

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

\begin{document}

\maketitle

\begin{frame}

\frametitle{Outline}

\label{sec-1}

\begin{itemize}

\item Creating dictionaries

\begin{itemize}

\item empty dictionaries

\item with data

\end{itemize}

\item Keys and values

\item Checking for elements

\item Iterating over elements

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Overview of Dictionaries}

\label{sec-2}

\begin{itemize}

\item A dictionary contains meaning of words

\begin{itemize}

\item \emph{Word} is the \emph{key} here.

\item \emph{Meaning} is the \emph{value} here.

\end{itemize}

\item A Key-Value pair data structure

\begin{itemize}

\item Provide key-value mappings

\end{itemize}

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Creating dictionary}

\label{sec-3}

\begin{itemize}

\item Empty dictionary

\begin{itemize}

\item \texttt{mt\_dict = \{\}}

\begin{itemize}

\item \texttt{[]} - lists

\item \texttt{\{\}} - dictionaries

\end{itemize}

\end{itemize}

\item With data

\begin{verbatim}

extensions = {'jpg' : 'JPEG Image', 

              'py' : 'Python script',

              'html' : 'Html document', 

              'pdf' : 'Portable Document Format'}

\end{verbatim}

   \textbf{Note} - ordering in dictionaries cannot be relied on

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Accessing Elements}

\label{sec-4}

\begin{itemize}

\item syntax

\begin{verbatim}

     extensions[key]

\end{verbatim}

\end{itemize}

\begin{verbatim}

   In []: print extensions['jpg']

   Out []: JPEG Image

   In []: print extensions['zip']

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

\frametitle{Adding and Deleting values}

\label{sec-5}

\begin{itemize}

\item Adding a new value

\begin{verbatim}

     In []: extension['cpp'] = 'C++ code'

\end{verbatim}

    adds a new key \emph{cpp} with \emph{C++ code} as value

\item Deleting values

\begin{verbatim}

     In []: del extensions['pdf']

\end{verbatim}

    deletes the key-value pair identified by \emph{pdf}

\item Changing value associated with a key

\begin{verbatim}

     In []: extension['cpp'] = 'C++ source code'

\end{verbatim}

    changes the value of the existing key

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Checking for container-ship of keys}

\label{sec-6}

\begin{verbatim}

   In []: 'py' in extensions

   Out []: True

\end{verbatim}

  Returns \textbf{True} if the \emph{key} is found.

\begin{verbatim}

   In []: 'odt' in extensions

   Out []: False

\end{verbatim}

  Returns \textbf{False} if the \emph{key} is not found.

\end{frame}

\begin{frame}[fragile]

\frametitle{Retrieve keys and values}

\label{sec-7}

\begin{itemize}

\item \texttt{.keys()} method

\begin{verbatim}

     In []: extensions.keys()

\end{verbatim}

    Returns a list of keys in the dictionary.

\item \texttt{.values()} method

\begin{verbatim}

     In []: extensions.values()

\end{verbatim}

    Returns the list of values in the dictionary.

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Exercise 1}

\label{sec-8}

  Print the keys and values in the dictionary one by one.

\end{frame}

\begin{frame}

\frametitle{Summary}

\label{sec-9}

\begin{itemize}

\item Creating dictionaries

\begin{itemize}

\item empty dictionaries

\item with data

\end{itemize}

\item \texttt{.keys()} method

\item \texttt{.values()} method

\item Iterating over dictionaries

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Thank you!}

\label{sec-10}

  \begin{block}{}

  \begin{center}

  This spoken tutorial has been produced by the

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

  \end{center}

  \begin{center}

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

      Information \& Communication Technology \\ 

      MHRD, Govt. of India}.

  \end{center}  

  \end{block}

\end{frame}

\end{document}