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% Tutorial slides on Python.

%

% Author: Prabhu Ramachandran <prabhu at aero.iitb.ac.in>

% Copyright (c) 2005-2008, Prabhu Ramachandran

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% Taken from Fernando's slides.

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\usepackage{listings}

\lstset{language=Python,

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    commentstyle=\color{red}\itshape,

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% Title page

\title[Basic Python]{Python,\\a great programming toolkit:\\

numerics and plotting}

\author[Asokan \& Prabhu] {Asokan Pichai\\Prabhu Ramachandran}

\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}

\date[] {26, July 2009}

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%% Delete this, if you do not want the table of contents to pop up at

%% the beginning of each subsection:

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  \begin{frame}<beamer>

    \frametitle{Outline}

    \tableofcontents[currentsection,currentsubsection]

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  \begin{frame}<beamer>

    \frametitle{Outline}

    \tableofcontents[currentsection,currentsubsection]

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% DOCUMENT STARTS

\begin{document}

\begin{frame}

  \frametitle{Outline}

  \tableofcontents

\end{frame}

\section{Pythonicity}

\begin{frame}[fragile]

    \frametitle{The Zen of Python}

Try this!

\begin{lstlisting}

>>> import this

\end{lstlisting}

\end{frame}

\begin{frame}

    {Style Guide}

    Read PEP8

    \url{http://www.python.org/dev/peps/pep-0008/}

    \inctime{10}

\end{frame}

\section{More Python Machinery}

\subsection{Objects}

\begin{frame}{Objects in Python}

    \begin{itemize}

        \item What is an Object? (Types and classes)

        \item identity

        \item type

        \item method

      \end{itemize}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Why are they useful?}

  \small

  \begin{lstlisting}

for element in (1, 2, 3):

    print element

for key in {'one':1, 'two':2}:

    print key

for char in "123":

    print char

for line in open("myfile.txt"):

    print line

for line in urllib2.urlopen('http://site.com'):

    print line

  \end{lstlisting}

\end{frame}

\begin{frame}{And the winner is \ldots OBJECTS!}

  All objects providing a similar inteface can be used the same way.\\

  Functions (and others) are first-class objects. Can be passed to and returned from functions.

  \inctime{10}

\end{frame}

\subsection{Dictionary}

\begin{frame}{Dictionary}

  \begin{itemize}

    \item aka associative arrays, key-value pairs, hashmaps, hashtables \ldots    

    \item \typ{ d = \{ ``Hitchhiker's guide'' : 42, ``Terminator'' : ``I'll be back''\}}

    \item lists and tuples index: 0 \ldots n

    \item dictionaries index using strings

    \item aka key-value pairs

    \item what can be keys?

  \end{itemize}

\end{frame}

\begin{frame}{Dict \ldots }

  \begin{itemize}

    \item \alert{Unordered}

      \begin{block}{Standard usage}

        for key in dict:\\

            <use> dict[key] \# => value

      \end{block}

    \item \typ{d.keys()} returns a list

    \item can we have duplicate keys?

  \end{itemize}

\end{frame}

\begin{frame} {Problem Set 2.1}

  \begin{description}

\item[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 function that takes such a string and returns a tuple (yyyy, mm, dd) where all three elements are ints.

    \item[2.1.2] Count word frequencies in a file.

    \item[2.1.3] Find the most used Python keywords in your Python code (import keyword).

\end{description}

\inctime{20}

\end{frame}

\subsection{Set}

\begin{frame}[fragile]

  \frametitle{Set}

    \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}

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

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

f10|p10, f10&p10

f10-p10, p10-f10, f10^p10

set([2,3]) < p10, set([2,3]) <= p10

2 in p10, 4 in p10

len(f10)

\end{lstlisting}

\end{frame}

\begin{frame}

  \frametitle{Problem set 2.2}

  \begin{description}

    \item[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?

    \item[2.2.2] Given a string of the form ``4-7, 9, 12, 15'' find the numbers missing in this list for a given range.

\end{description}

\inctime{15}

\end{frame}

\subsection{Functions Reloaded!}

\begin{frame}[fragile]

    \frametitle{Advanced functions}

    \begin{itemize}

        \item default args

        \item varargs

        \item keyword args

        \item scope

        \item \typ{global}

      \end{itemize}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Functions: default arguments}

  \begin{lstlisting}

def ask_ok(prompt, retries=4, complaint='Yes or no!'):

    while True:

        ok = raw_input(prompt)

        if ok in ('y', 'ye', 'yes'): 

            return True

        if ok in ('n', 'no', 'nop', 'nope'): 

            return False

        retries = retries - 1

        if retries < 0: 

            raise IOError, 'bad user'

        print complaint

  \end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Functions: keyword arguments}

  \small

  \begin{lstlisting}

def parrot(voltage, state='a stiff', 

           action='voom', type='Royal Blue'):

    print "-- This parrot wouldn't", action,

    print "if you supply", voltage, "Volts."

    print "-- Lovely plumage, the", type

    print "-- It's", state, "!"

parrot(1000)

parrot(action = 'VOOOOOM', voltage = 1000000)

parrot('a thousand', state = 'pushing up the daisies')

parrot('a million', 'bereft of life', 'jump')

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Functions: arbitrary argument lists}

  \begin{itemize}

  \item Arbitrary number of arguments using \verb+*args+ or

    \verb+*whatever+

  \item Keyword arguments using \verb+**kw+

  \item Given a tuple/dict how do you call a function?

    \begin{itemize}

    \item Using argument unpacking

    \item For positional arguments: \verb+foo(*[5, 10])+

    \item For keyword args: \verb+foo(**{'a':5, 'b':10})+

    \end{itemize}

  \end{itemize}

\end{frame}

  \begin{frame}[fragile]

\begin{lstlisting}

def foo(a=10, b=100):

    print a, b

def func(*args, **keyword):

    print args, keyword

# Unpacking:

args = [5, 10]

foo(*args)

kw = {'a':5, 'b':10}

foo(**kw)

\end{lstlisting}

    \inctime{15} 

\end{frame}

\subsection{Functional programming}

\begin{frame}[fragile]

    \frametitle{Functional programming}

What is the basic idea?\\

Why is it interesting?\\

\typ{map, reduce, filter}\\

list comprehension\\

generators

    \inctime{10} 

\end{frame}

\end{document}

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