path: root/day2/session2.tex

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%Tutorial slides on Python.
%
% Author: FOSSEE 
% Copyright (c) 2009, FOSSEE, IIT Bombay
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% Taken from Fernando's slides.
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\usepackage{listings}
\lstset{language=Python,
    basicstyle=\ttfamily\bfseries,
    commentstyle=\color{red}\itshape,
  stringstyle=\color{darkgreen},
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% Title page
\title[Basic Python]{Python language: Data structures and functions}

\author[FOSSEE Team] {The FOSSEE Group}

\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
\date[] {SciPy.in 2010, Tutorials}
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%\pgfdeclareimage[height=0.75cm]{iitmlogo}{iitmlogo}
%\logo{\pgfuseimage{iitmlogo}}


%% Delete this, if you do not want the table of contents to pop up at
%% the beginning of each subsection:
\AtBeginSubsection[]
{
  \begin{frame}<beamer>
    \frametitle{Outline}
    \tableofcontents[currentsection,currentsubsection]
  \end{frame}
}

\AtBeginSection[]
{
  \begin{frame}<beamer>
    \frametitle{Outline}
    \tableofcontents[currentsection,currentsubsection]
  \end{frame}
}

% If you wish to uncover everything in a step-wise fashion, uncomment
% the following command: 
%\beamerdefaultoverlayspecification{<+->}

%\includeonlyframes{current,current1,current2,current3,current4,current5,current6}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% DOCUMENT STARTS
\begin{document}

\begin{frame}
  \titlepage
\end{frame}

\begin{frame}
  \frametitle{Outline}
  \tableofcontents
  % You might wish to add the option [pausesections]
\end{frame}

\section{Data structures}
\subsection{Lists}
\begin{frame}[fragile]
  \frametitle{Lists}
\begin{block}{We already know that}
  \begin{lstlisting}
num = [1, 2, 3, 4]
  \end{lstlisting}
is a list
\end{block}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Lists: methods}
  \begin{lstlisting}
In []: num = [9, 8, 2, 3, 7]

In []: num + [4, 5, 6]
Out[]: [9, 8, 2, 3, 7, 4, 5, 6]

In []: num.append([4, 5, 6])

In []: num
Out[]: [9, 8, 2, 3, 7, [4, 5, 6]]
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Lists: methods}
  \begin{lstlisting}
In []: num = [9, 8, 2, 3, 7]

In []: num.extend([4, 5, 6])
In []: num
Out[]: [9, 8, 2, 3, 7, 4, 5, 6]

In []: num.reverse()
In []: num
Out[]: [6, 5, 4, 7, 3, 2, 8, 9]

In []: num.remove(6)
In []: num
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
\frametitle{List containership}
\emphbar{Recall \typ{num} is \typ{[9, 8, 2, 3, 7]}}
\begin{lstlisting}
In []: 4 in num
Out[]: False

In []: b = 8
In []: b in num
Out[]: True

In []: b not in num
Out[]: False
\end{lstlisting}
\end{frame}

\subsection{Tuples}
\begin{frame}[fragile]
\frametitle{Tuples: Immutable lists}
\begin{lstlisting}
In []: t = (1, 2, 3, 4, 5, 6, 7, 8)

In []: t[0] + t[3] + t[-1]
Out[]: 13

In []: t[4] = 7 
\end{lstlisting}
\pause
\begin{block}{Note:}
\begin{itemize}
  \item Tuples are immutable - cannot be changed
\end{itemize}
\end{block}

\end{frame}

\begin{frame}
  {A classic problem}
  \begin{block}
    {Interchange values}
    How to interchange values of two variables? 
  \end{block}
  \pause
  \begin{block}{Note:}
    This Python idiom works for all types of variables.\\
They need not be of the same type!
  \end{block}
\end{frame}

\subsection{Dictionaries}

\begin{frame}[fragile]
  \frametitle{Dictionaries: Introduction}
  \begin{itemize}
    \item Lists index using integers\\
Recall \typ{p = [2, 3, 5, 7]} and\\
\typ{p[1]} is equal to \typ{3}
    \item Dictionaries index using strings
  \end{itemize}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Dictionaries \ldots}
  \begin{lstlisting}
In []: d = {'png' : 'image file',
      'txt' : 'text file', 
      'py' : 'python code',
      'java': 'bad code', 
      'cpp': 'complex code'}

In []: d['txt']
Out[]: 'text file'
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Dictionaries \ldots}
  \begin{lstlisting}
In []: 'py' in d
Out[]: True

In []: 'jpg' in d
Out[]: False
  \end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Dictionaries \ldots}
  \begin{small}
    \begin{lstlisting}
In []: d.keys()
Out[]: ['cpp', 'py', 'txt', 'java', 'png']

In []: d.values()
Out[]: ['complex code', 'python code',
        'text file', 'bad code', 
        'image file']
    \end{lstlisting}
  \end{small}
%%  \inctime{10}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Inserting elements into dictionary}
  \emphbar{\alert{\typ{d[key] = value}}}
  \begin{lstlisting}
In []: d['bin'] = 'binary file'
In []: d
Out[]: 
{'bin': 'binary file',
 'cpp': 'complex code',
 'java': 'bad code',
 'png': 'image file',
 'py': 'python code',
 'txt': 'text file'}
  \end{lstlisting}
  \emphbar{\alert{Duplicate keys are overwritten!}}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Dictionaries: containership}
  \begin{lstlisting}
In []: 'bin' in d
Out[]: True

In []: 'hs' in d
Out[]: False
  \end{lstlisting}
  \begin{block}{Note}
    \begin{itemize}
      \item We can check for the containership of keys only
      \item Not values
    \end{itemize}
  \end{block}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Dictionaries: methods}
  \begin{lstlisting}
In []: d.keys()
Out[]: ['bin', 'java', 'py', 'cpp', 'txt', 'png']

In []: d.values()
Out[]: 
['binary file',
 'bad code',
 'python code',
 'complex code',
 'text file',
 'image file']
  \end{lstlisting}
\end{frame}

\begin{frame} {Problem Set 2.1: Problem 2.1.1}
You are given date strings of the form ``29 Jul, 2009'', or ``4 January 2008''. In other words a number, a string and another number, with a comma sometimes separating the items.\\Write a program that takes such a string as input and prints a tuple (yyyy, mm, dd) where all three elements are ints.
\end{frame}

\subsection{Sets}
\begin{frame}[fragile]
  \frametitle{Sets}
    \begin{itemize}
      \item Simplest container, mutable
      \item No ordering, no duplicates
      \item usual suspects: union, intersection, subset \ldots
      \item >, >=, <, <=, in, \ldots
    \end{itemize}
    \begin{lstlisting}

In []: f10 = set([1,2,3,5,8])

In []: p10 = set([2,3,5,7])

In []: f10 | p10
Out[]: set([1, 2, 3, 5, 7, 8])
\end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Set \ldots}
    \begin{lstlisting}
In []: f10 & p10
Out[]: set([2, 3, 5])

In []: f10 - p10
Out[]: set([1, 8])

In []: p10 - f10, f10 ^ p10
Out[]: (set([7]), set([1, 7, 8]))

In []: set([2,3]) < p10
Out[]: True
\end{lstlisting}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Set \ldots}
    \begin{lstlisting}
In []: set([2,3]) <= p10
Out[]: True

In []: 2 in p10
Out[]: True

In []: 4 in p10
Out[]: False

In []: len(f10)
Out[]: 5
\end{lstlisting}
\end{frame}

\begin{frame}
  \frametitle{Problem set 2.2: Problem 2.2.1}
Given a dictionary of the names of students and their marks, identify how many duplicate marks are there? and what are these?
\end{frame}

\begin{frame}
  \frametitle{Problem 2.2.2}
Given a list of words, find all the anagrams in the list.

\end{frame}

\begin{frame}
  \frametitle{What did we learn?}
  \begin{itemize}
    \item Advanced Data structures:
    \begin{itemize}
      \item Lists
      \item Tuples
      \item Dictionaries
      \item Sets
    \end{itemize}
  \end{itemize}
\end{frame}

\end{document}

%% Questions for Quiz %%
%% ------------------ %%

\begin{frame}
    \frametitle{\incqno}
  How do you find the presence of an element \emph{x} in the list \emph{a}?
\end{frame}


\begin{frame}[fragile]
    \frametitle{\incqno}
  \begin{lstlisting}
In []: set([1, 2, 8, 2, 13, 8, 9])
  \end{lstlisting}
  What is the output?
\end{frame}

\begin{frame}[fragile]
    \frametitle{\incqno}
  \begin{lstlisting}
In []: a = {'a': 1, 'b': 2} 
In []: a['a'] = 10
In []: print a
  \end{lstlisting}
  What is the output?
\end{frame}

\begin{frame}[fragile]
    \frametitle{\incqno}
  \begin{lstlisting}
In []: for i in range(3, 10, 2):
  ...:     print i
  \end{lstlisting}
  What is the output?
\end{frame}

\begin{frame}[fragile]
    \frametitle{\incqno}
  \begin{lstlisting}
In []: a = [1, 2, 3] 
In []: a.extend([5, 6])
  \end{lstlisting}
  What is the value of a?
\end{frame}

\begin{frame}[fragile]
    \frametitle{\incqno}
  \begin{lstlisting}
In []: a = (1, 2, 3)
In []: a[1] = 10
  \end{lstlisting}
  What is the result?
\end{frame}

\begin{frame}[fragile]
    \frametitle{\incqno}
  \begin{lstlisting}
def func(x, y=10):
    print x+1, y+10

func(1)

  \end{lstlisting}
  What is the output?
\end{frame}