1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

     2 % Tutorial slides on Python.

     3 %

     4 % Author: Prabhu Ramachandran <prabhu at aero.iitb.ac.in>

     5 % Copyright (c) 2005-2008, Prabhu Ramachandran

     6 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

     7 

     8 \documentclass[14pt,compress]{beamer}

     9 %\documentclass[draft]{beamer}

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    15 \mode<presentation>

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    22 \usepackage[english]{babel}

    23 \usepackage[latin1]{inputenc}

    24 %\usepackage{times}

    25 \usepackage[T1]{fontenc}

    26 

    27 % Taken from Fernando's slides.

    28 \usepackage{ae,aecompl}

    29 \usepackage{mathpazo,courier,euler}

    30 \usepackage[scaled=.95]{helvet}

    31 

    32 \definecolor{darkgreen}{rgb}{0,0.5,0}

    33 

    34 \usepackage{listings}

    35 \lstset{language=Python,

    36     basicstyle=\ttfamily,

    37     commentstyle=\color{red}\itshape,

    38   stringstyle=\color{darkgreen},

    39   showstringspaces=false,

    40   keywordstyle=\color{blue}\bfseries}

    41 

    42 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    43 % Macros

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    53 

    54 \newcommand{\typ}[1]{\texttt{#1}}

    55 

    56 \newcommand{\kwrd}[1]{ \texttt{\textbf{\color{blue}{#1}}}  }

    57 

    58 %%% This is from Fernando's setup.

    59 % \usepackage{color}

    60 % \definecolor{orange}{cmyk}{0,0.4,0.8,0.2}

    61 % % Use and configure listings package for nicely formatted code

    62 % \usepackage{listings}

    63 % \lstset{

    64 %    language=Python,

    65 %    basicstyle=\small\ttfamily,

    66 %    commentstyle=\ttfamily\color{blue},

    67 %    stringstyle=\ttfamily\color{orange},

    68 %    showstringspaces=false,

    69 %    breaklines=true,

    70 %    postbreak = \space\dots

    71 % }

    72 

    73 

    74 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    75 % Title page

    76 \title[Basic Python]{Python:\\A great programming toolkit}

    77 

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

    79 

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

    81 \date[] {10, August 2009}

    82 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    83 

    84 %\pgfdeclareimage[height=0.75cm]{iitmlogo}{iitmlogo}

    85 %\logo{\pgfuseimage{iitmlogo}}

    86 

    87 

    88 %% Delete this, if you do not want the table of contents to pop up at

    89 %% the beginning of each subsection:

    90 \AtBeginSubsection[]

    91 {

    92   \begin{frame}<beamer>

    93     \frametitle{Outline}

    94     \tableofcontents[currentsection,currentsubsection]

    95   \end{frame}

    96 }

    97 

    98 

    99 % If you wish to uncover everything in a step-wise fashion, uncomment

   100 % the following command: 

   101 %\beamerdefaultoverlayspecification{<+->}

   102 

   103 %\includeonlyframes{current,current1,current2,current3,current4,current5,current6}

   104 

   105 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   106 % DOCUMENT STARTS

   107 \begin{document}

   108 

   109 \begin{frame}

   110   \titlepage

   111 \end{frame}

   112 \begin{frame}

   113   {Acknowledgements}

   114   \begin{center}

   115   This program is conducted by\\

   116   IIT, Bombay\\

   117   through CDEEP\\as part of  the open source initiatives\\

   118   under the aegis of\\

   119   \alert{National Mission on Education through ICT,} \\

   120   Ministry of HRD.

   121   \end{center}

   122 \end{frame}

   123 

   124 \begin{frame}

   125   \frametitle{Outline}

   126   \tableofcontents

   127   % You might wish to add the option [pausesections]

   128 \end{frame}

   129 

   130 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   131 % TODO

   132 %

   133 %  * Add slide on Python packages (modules)

   134 %  * Add slides on reference counting.

   135 

   136 \section{Agenda}

   137 \begin{frame}{About the Workshop}

   138   \begin{description}

   139 	\item[Day 1, Session 1] Sat 09:30--11:00

   140 	\item[Day 1, Session 2] Sat 11:15--12:45

   141 	\item[Day 1, Session 3] Sat 13:45--15:15

   142 	\item[Day 1, Session 4] Sat 15:30--17:00

   143         \item[Day 2, Session 1] Sun 09:30--11:00

   144 	\item[Day 2, Session 2] Sun 11:15--12:45

   145 	\item[Day 2, Session 3] Sun 13:45--15:15

   146 	\item[Day 2, Session 4] Sun 15:30--17:00

   147   \end{description}

   148 \end{frame}

   149 

   150 \section{Agenda}

   151 \begin{frame}{About the Workshop}

   152   \begin{block}{Goal of the workshop}

   153 	At the end of this program, successful participants will be able to use python as their scripting and problem solving language. Aimed at Engg. students--focus on basic numerics and plotting-- but should serve a similar purpose for others. 

   154   \end{block}

   155 \end{frame}

   156 

   157 \begin{frame}{Checklist}

   158   Let us verify that all of us are having the same (similar) tools and environment

   159   \begin{description}

   160 	\item[python] Type python at the command line. Do you see version 2.5 or later?

   161 	\item[IPython] Is IPython available?

   162 	\item[Editor] Which editor? scite, vim, emacs, \ldots

   163   \end{description}

   164 \end{frame}

   165 

   166 \section{Overview}

   167 \begin{frame}{Session 1}

   168   \begin{itemize}

   169 	\item Introduction and motivation

   170 	\item Using the interpreter(s)

   171 	\item Basic data types: int, float, string

   172 	\item Basic data structures: list

   173 	\item Basic console IO: \texttt{raw\_input(), print}

   174     \item Basic control flow: \texttt{if, while}

   175 	\item Problem set 1

   176     \item Functions $\rightarrow$ Problem set 2

   177     \item lists, \texttt{for}  $\rightarrow$ Problem set 3

   178     \item IO, Modules $\rightarrow$ Problem sets 4,5, \ldots

   179   \end{itemize}

   180 \end{frame}

   181 

   182 \begin{frame}

   183   \frametitle{Introduction}

   184   \begin{itemize}

   185   \item Creator and BDFL: Guido van Rossum

   186   \item Conceived in December 1989

   187   \item ``Python'' as in Monty Python's Flying Circus

   188   \item Current stable version of Python is 2.6.x

   189   \item PSF license (like BSD: no strings attached)

   190   \item Highly cross platform

   191   \item Runs on the Nokia series 60!

   192   \item \alert{Philosophy:} Simple and complete by design

   193   \end{itemize}

   194 \end{frame}

   195 

   196 \begin{frame}

   197   \frametitle{Resources}

   198   \begin{itemize}

   199   \item Part of many GNU/Linux distributions

   200   \item Web: \url{http://www.python.org}

   201   \item Doc: \url{http://www.python.org/doc}

   202   \item Free Tutorials:

   203     \begin{itemize}

   204     \item Official Python tutorial: \url{http://docs.python.org/tut/tut.html}

   205     \item Byte of Python: \url{http://www.byteofpython.info/}

   206     \item Dive into Python: \url{http://diveintopython.org/}

   207     \end{itemize}

   208   \end{itemize}

   209 \end{frame}

   210 

   211 \begin{frame}

   212   \frametitle{Why Python?}

   213   \begin{itemize}

   214   \item Designed to be readable and easy to use

   215   \item High level, interpreted, modular, OO

   216   \item Much faster development cycle

   217   \item Powerful interactive environment

   218   \item Rapid application development

   219   \item Rich standard library and modules

   220   \item Interfaces well with C++, C and FORTRAN

   221   \item \alert{More than a math package $\Rightarrow$ some extra work compared to math packages}

   222   \end{itemize}

   223 \end{frame}

   224 

   225 \begin{frame}

   226   \frametitle{Use cases}

   227   \begin{itemize}

   228   \item NASA: Space Shuttle Mission Design

   229   \item AstraZeneca: Collaborative Drug Discovery

   230   \item ForecastWatch.com: Helps Meteorologists

   231   \item Industrial Light \& Magic: Runs on Python

   232   \item Zope: Commercial grade Toolkit

   233   \item Plone: Professional high feature CMS

   234   \item RedHat: install scripts, sys-admin tools

   235   \item Django: A great web application framework

   236   \item Google: A strong python shop

   237   \end{itemize}

   238 \end{frame}

   239 

   240 \begin{frame}

   241   \frametitle{To sum up, python is\ldots}

   242   \begin{itemize}

   243   \item dynamically typed, interpreted $\rightarrow$ rapid testing/prototyping

   244   \item powerful, very high level

   245   \item has full introspection 

   246   \item Did we mention powerful?

   247   \end{itemize}

   248   \begin{block}{But \ldots}

   249     may be wanting in performance. specialised resources such as SWIG, \alert{Cython} are available 

   250   \end{block}

   251   \inctime{15}

   252 \end{frame}

   253 

   254 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   255 % TIME: 15 m, running 15m

   256 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   257 

   258 \section{Python}

   259 

   260 \subsection{Getting Started}

   261 

   262 \begin{frame}[fragile]{At the prompt, type the following}

   263    \begin{lstlisting}

   264 >>> print 'Hello Python' 

   265 >>> print 3124 * 126789

   266 >>> 1786 % 12

   267 >>> 3124 * 126789

   268 >>> a = 3124 * 126789

   269 >>> big = 12345678901234567890 ** 3

   270 >>> verybig = big * big * big * big 

   271 >>> 12345**6, 12345**67, 12345**678

   272   \end{lstlisting}

   273 \end{frame}

   274 

   275 \begin{frame}[fragile]{At the prompt, type the following}

   276    \begin{lstlisting}

   277 >>> s = 'Hello '

   278 >>> p = 'World'

   279 >>> s + p 

   280 >>> s * 12 

   281 >>> s * s

   282 >>> s + p * 12, (s + p)* 12

   283 >>> s * 12 + p * 12

   284 >>> 12 * s 

   285     \end{lstlisting}

   286 \end{frame}

   287 

   288 \begin{frame}[fragile]{At the prompt, type the following}

   289   \begin{lstlisting}

   290 >>> 17/2

   291 >>> 17/2.0

   292 >>> 17.0/2

   293 >>> 17.0/8.5

   294 >>> int(17/2.0)

   295 >>> float(17/2)

   296 >>> str(17/2.0)

   297 >>> round( 7.5 )

   298   \end{lstlisting}

   299   \begin{block}{Mini exercise}

   300 	Round a float to the nearest integer, using \texttt{int()}?

   301   \end{block}

   302 \end{frame}

   303 

   304 \begin{frame}{Midi exercises}

   305   \begin{center}

   306     \begin{itemize}

   307       \item What does this do?

   308       \item \texttt{round(amount * 10) /10.0 }

   309     \end{itemize}

   310   \end{center}

   311 \end{frame}

   312 

   313 \begin{frame}{More exercises?}

   314   \begin{center}

   315     \begin{block}{Round sums}

   316       How to round a number to the nearest  5 paise?\\

   317       \begin{description}

   318         \item[Remember] 17.23 $\rightarrow$ 17.25,\\ while 17.22 $\rightarrow$ 17.20\\

   319       \end{description}

   320       How to round a number to the nearest 20 paise?

   321     \end{block}

   322   \end{center}

   323 \end{frame}

   324 

   325 \begin{frame}[fragile] {A question of good style}

   326   \begin{lstlisting}

   327     amount = 12.68

   328     denom = 0.05

   329     nCoins = round(amount/denom)

   330     rAmount = nCoins * denom

   331   \end{lstlisting}

   332   \pause

   333   \begin{block}{Style Rule \#1}

   334     Naming is 80\% of programming

   335   \end{block}

   336 \end{frame}

   337 

   338 

   339 \begin{frame}[fragile]

   340   \frametitle{Odds and ends}

   341   \begin{itemize}

   342     \item Case sensitive

   343     \item Dynamically typed $\Rightarrow$ need not specify a type

   344       \begin{lstlisting}

   345 a = 1

   346 a = 1.1

   347 a = "Now I am a string!"

   348       \end{lstlisting}

   349     \item Comments:

   350       \begin{lstlisting}

   351 a = 1  # In-line comments

   352 # Comment in a line to itself.

   353 a = "# This is not a comment!"

   354       \end{lstlisting}

   355   \end{itemize}

   356   \inctime{15}

   357 \end{frame}

   358 

   359 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   360 % TIME: 15 m, running 30m

   361 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   362 

   363 \subsection{Data types}

   364 \begin{frame}

   365   \frametitle{Basic types}

   366   \begin{itemize}

   367     \item numbers: float, int, long, complex

   368     \item strings

   369     \item boolean

   370   \end{itemize}

   371   \begin{block}{Also to be discussed later}

   372     tuples, lists, dictionaries, functions, objects\ldots

   373   \end{block}

   374 \end{frame}

   375 

   376 \begin{frame}[fragile]

   377   \frametitle{Numbers}

   378   \vspace*{-0.25in}

   379   \begin{lstlisting}

   380 >>> a = 1 # Int.

   381 >>> l = 1000000L # Long

   382 >>> e = 1.01325e5 # float

   383 >>> f = 3.14159 # float

   384 >>> c = 1+1j # Complex!

   385 >>> print f*c/a

   386 (3.14159+3.14159j)

   387 >>> print c.real, c.imag

   388 1.0 1.0

   389 >>> abs(c)

   390 1.4142135623730951

   391 >>> abs( 8 - 9.5 )

   392 1.5

   393   \end{lstlisting}

   394 \end{frame}

   395 

   396 \begin{frame}[fragile]

   397   \frametitle{Boolean}

   398   \begin{lstlisting}

   399 >>> t = True

   400 >>> f = not t

   401 False

   402 >>> f or t

   403 True

   404 >>> f and t

   405 False

   406   \end{lstlisting}

   407   \begin{block}{Try:}

   408   NOT True\\

   409   not TRUE

   410   \end{block}

   411 \end{frame}

   412 

   413 \begin{frame}[fragile]

   414   \frametitle{Relational and logical operators}

   415   \begin{lstlisting}

   416 >>> a, b, c = -1, 0, 1

   417 >>> a == b

   418 False

   419 >>> a <= b 

   420 True

   421 >>> a + b != c

   422 True

   423 >>> a < b < c

   424 True

   425 >>> c >= a + b

   426 True

   427   \end{lstlisting}

   428 \end{frame}

   429 

   430 \begin{frame}[fragile]

   431   \frametitle{Strings}

   432   \begin{lstlisting}

   433 s = 'this is a string'

   434 s = 'This one has "quotes" inside!'

   435 s = "I have 'single-quotes' inside!"

   436 l = "A string spanning many lines\

   437 one more line\

   438 yet another"

   439 t = """A triple quoted string does

   440 not need to be escaped at the end and 

   441 "can have nested quotes" etc."""

   442   \end{lstlisting}

   443 \end{frame}

   444 

   445 \begin{frame}[fragile]

   446   \frametitle{More Strings}

   447   \vspace*{-0.2in}

   448   \begin{lstlisting}

   449 >>> w = "hello"    

   450 >>> print w[0] + w[2] + w[-1]

   451 hlo

   452 >>> len(w) # guess what

   453 5

   454 >>> s = u'Unicode strings!'

   455 >>> # Raw strings (note the leading 'r')

   456 ... r_s = r'A string $\alpha \nu$'

   457   \end{lstlisting}

   458 \pause

   459   \begin{lstlisting}

   460 >>> w[0] = 'H' # Can't do that!

   461 Traceback (most recent call last):

   462   File "<stdin>", line 1, in ?

   463 TypeError: object does not support item assignment

   464   \end{lstlisting}

   465 \end{frame}

   466 

   467 \begin{frame}

   468   \frametitle{Let us switch to IPython}

   469   Why?

   470   \begin{block}

   471     {Better help (and a lot more)}

   472     Tab completion\\

   473     ?\\

   474     .?\\

   475     object.function?

   476   \end{block}

   477 \end{frame}

   478 

   479 \begin{frame}[fragile]

   480   \frametitle{More on strings}

   481   \begin{lstlisting}

   482 In [1]: a = 'hello world'

   483 In [2]: a.startswith('hell')

   484 Out[2]: True

   485 In [3]: a.endswith('ld')

   486 Out[3]: True

   487 In [4]: a.upper()

   488 Out[4]: 'HELLO WORLD'

   489 In [5]: a.upper().lower()

   490 Out[5]: 'hello world'

   491   \end{lstlisting}

   492 \end{frame}

   493 

   494 \begin{frame}[fragile]{Still with strings}

   495   \begin{lstlisting}

   496 In [6]: a.split()

   497 Out[6]: ['hello', 'world']

   498 In [7]: ''.join(['a', 'b', 'c'])

   499 Out[7]: 'abc'

   500 In [8] 'd' in ''.join( 'a', 'b', 'c')

   501 Out[8]: False

   502   \end{lstlisting}

   503   \begin{block}{Try:}

   504     \texttt{a.split( 'o' )}\\

   505     \texttt{'x'.join( a.split( 'o' ) )}

   506   \end{block}

   507 \end{frame}

   508 

   509 \begin{frame}[fragile]{Surprise! strings!!}

   510   \begin{lstlisting}

   511 In [11]: x, y = 1, 1.2

   512 In [12]: 'x is %s, y is %s' %(x, y)

   513 Out[12]: 'x is 1, y is 1.234'

   514   \end{lstlisting}

   515   \begin{block}{Try:}

   516     \texttt{'x is \%d, y is \%f' \%(x, y) }\\

   517     \texttt{'x is \%3d, y is \%4.2f' \%(x, y) }

   518   \end{block}

   519   \small

   520 \url{docs.python.org/lib/typesseq-strings.html}\\

   521 \end{frame}

   522 

   523 \begin{frame}

   524   {Interlude}

   525   \begin{block}

   526     {A classic problem}

   527     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!

   528   \end{block}

   529   \inctime{30}

   530 \end{frame}

   531 

   532 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   533 % TIME: 25 m+ Interlude break 5 mins, running 60m 

   534 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   535 

   536 \subsection{Control flow}

   537 \begin{frame}

   538   \frametitle{Control flow constructs}  

   539   \begin{itemize}

   540   \item \kwrd{if/elif/else}: branching

   541   \item \kwrd{while}: looping

   542   \item \kwrd{for}: iterating 

   543   \item \kwrd{break, continue}: modify loop 

   544   \item \kwrd{pass}: syntactic filler

   545   \end{itemize}

   546 \end{frame}

   547 

   548 \begin{frame}[fragile]

   549   \frametitle{Basic conditional flow}

   550   \begin{lstlisting}

   551 In [21]: a = 7

   552 In [22]: b = 8

   553 In [23]: if a > b:

   554    ....:    print 'Hello'

   555    ....: else:

   556    ....:     print 'World'

   557    ....:

   558    ....:

   559 World

   560   \end{lstlisting}

   561   Let us switch to creating a file

   562 \end{frame}

   563 

   564 \begin{frame}

   565   {Creating python files}

   566   \begin{itemize}

   567     \item aka scripts

   568     \item use your editor

   569     \item Note that white space is the way to specify blocks!

   570     \item extension \typ{.py}

   571     \item run with \texttt{python hello.py} at the command line

   572     \item in IPython\ldots

   573   \end{itemize}

   574 \end{frame}

   575 

   576 \begin{frame}[fragile]

   577   \frametitle{\typ{If...elif...else} example}

   578 \begin{lstlisting}

   579 x = int(raw_input("Enter an integer:"))

   580 if x < 0:

   581      print 'Be positive!'

   582 elif x == 0:

   583      print 'Zero'

   584 elif x == 1:

   585      print 'Single'

   586 else:

   587      print 'More'

   588 \end{lstlisting}

   589 \end{frame}

   590 

   591 \begin{frame}{Simple IO}

   592   \begin{block}

   593     {Console Input}

   594     \texttt{raw\_input(}) waits for user input.\\Prompt string is optional.\\

   595     All keystrokes are Strings!\\\texttt{int()} converts string to int.

   596   \end{block}

   597   \begin{block}

   598     {Console output}

   599     \texttt{print} is straight forward. Major point to remember is the distinction between \texttt{print x} and \texttt{print x,}

   600   \end{block}

   601 \end{frame}

   602 

   603 \begin{frame}[fragile]

   604   \frametitle{Basic looping}

   605   \begin{lstlisting}

   606 # Fibonacci series:

   607 # the sum of two elements

   608 # defines the next

   609 a, b = 0, 1

   610 while b < 10:

   611     print b,

   612     a, b = b, a + b

   613  

   614 \end{lstlisting}

   615 \typ{1 1 2 3 5 8}\\  

   616 \alert{Recall it is easy to write infinite loops with \kwrd{while}}

   617   \inctime{20}

   618 \end{frame}

   619 

   620 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   621 % TIME: 20 m, running 80m 

   622 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   623 

   624 \begin{frame}

   625   \frametitle{Problem set 1}

   626   \begin{itemize}

   627     \item All the problems can be\\

   628       solved using \kwrd{if} and \kwrd{while} 

   629   \end{itemize}

   630 \end{frame}

   631 

   632 \begin{frame}{Problem 1.1}

   633   Write a program that displays all three digit numbers that are equal to the sum of the cubes of their digits. That is, print numbers $abc$ that have the property $abc = a^3 + b^3 + c^3$\\

   634 These are called $Armstrong$ numbers.

   635 \end{frame}

   636   

   637 \begin{frame}{Problem 1.2 - Collatz sequence}

   638 \begin{enumerate}

   639   \item Start with an arbitrary (positive) integer. 

   640   \item If the number is even, divide by 2; if the number is odd multiply by 3 and add 1.

   641   \item Repeat the procedure with the new number.

   642   \item It appears that for all starting values there is a cycle of 4, 2, 1 at which the procedure loops.

   643 \end{enumerate}

   644     Write a program that accepts the starting value and prints out the Collatz sequence.

   645 

   646 \end{frame}

   647 

   648 \begin{frame}{Problem 1.3 - Kaprekar's constant}

   649   \begin{enumerate}

   650     \item Take a four digit number--with at least two digits different.

   651     \item Arrange the digits in ascending and descending order, giving A and D respectively.

   652     \item Leave leading zeros in A!

   653     \item Subtract A from D.

   654     \item With the result, repeat from step 2.

   655   \end{enumerate}

   656   Write a program to accept a 4-digit number and display the progression to Kaprekar's constant.

   657 \end{frame}

   658 

   659 \begin{frame}[fragile]{Problem 1.4}

   660   Write a program that prints the following pyramid on the screen. 

   661   \begin{lstlisting}

   662 1

   663 2  2

   664 3  3  3

   665 4  4  4  4

   666   \end{lstlisting}

   667 The number of lines must be obtained from the user as input.\\

   668 \pause

   669 When can your code fail?

   670 \only<2->{\inctime{25}}

   671 \end{frame}

   672 

   673 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   674 % TIME: 25 m, running 105m 

   675 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   676 

   677 \subsection{Functions}

   678 \begin{frame}[fragile]

   679 \frametitle{Functions: examples}

   680   \begin{lstlisting}

   681 def signum( r ):

   682     """returns 0 if r is zero

   683     -1 if r is negative

   684     +1 if r is positive"""

   685     if r < 0:

   686         return -1

   687     elif r > 0:

   688         return 1

   689     else:

   690         return 0

   691   \end{lstlisting}

   692 \end{frame}

   693 

   694 \begin{frame}[fragile]

   695   \frametitle{Functions: examples}

   696   \begin{lstlisting}

   697 def pad( n, size ): 

   698     """pads integer n with spaces

   699     into a string of length size

   700     """

   701     SPACE = ' '

   702     s = str( n )

   703     padSize = size - len( s )

   704     return padSize * SPACE + s

   705   \end{lstlisting}

   706 \pause

   707 What about \%3d?

   708 \end{frame}

   709 

   710 \begin{frame}[fragile]

   711   {What does this function do?}

   712   \begin{lstlisting}

   713 def what( n ):

   714     if n < 0: n = -n

   715     while n > 0:

   716         if n % 2 == 1:

   717             return False

   718         n /= 10

   719     return True

   720   \end{lstlisting}

   721 \end{frame}

   722 

   723 \begin{frame}[fragile]

   724   {What does this function do?}

   725 \begin{lstlisting}

   726 def what( n ):

   727     i = 1    

   728     while i * i < n:

   729         i += 1

   730     return i * i == n, i

   731   \end{lstlisting}

   732 \end{frame}

   733 

   734 \begin{frame}[fragile]

   735   {What does this function do?}

   736   \begin{lstlisting}

   737 def what( n, x ):

   738     z = 1.0

   739     if n < 0:

   740         x = 1.0 / x

   741         n = -n

   742     while n > 0:

   743         if n % 2 == 1:

   744             z *= x

   745         n /= 2

   746         x *= x

   747     return z

   748   \end{lstlisting}

   749 \end{frame}

   750 

   751 \begin{frame}

   752   {Before writing a function}

   753   \begin{itemize}

   754       \item Builtin functions for various and sundry

   755       \item \typ{abs, any, all, len, max, min}

   756       \item \typ{pow, range, sum, type}

   757       \item Refer here:

   758           \url{http://docs.python.org/library/functions.html}

   759   \end{itemize}

   760   \inctime{15} 

   761 \end{frame}

   762 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   763 % TIME: 15 m, running 120m 

   764 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   765 

   766 \begin{frame}{Problem set 2}

   767   The focus is on writing functions and calling them.

   768 \end{frame}

   769 

   770 \begin{frame}{Problem 2.1}

   771   Write a function to return the gcd of two numbers.

   772 \end{frame}

   773 

   774 \begin{frame}{Problem 2.2}

   775 A pythagorean triad $(a,b,c)$ has the property $a^2 + b^2 = c^2$.\\By primitive we mean triads that do not `depend' on others. For example, (4,3,5) is a variant of (3,4,5) and hence is not primitive. And (10,24,26) is easily derived from (5,12,13) and should not be displayed by our program. \\

   776 Write a program to print primitive pythagorean triads. The program should generate all triads with a, b values in the range 0---100

   777 \end{frame}

   778 

   779 \begin{frame}{Problem 2.3}

   780   Write a program that generates a list of all four digit numbers that have all their digits even and are perfect squares.\\For example, the output should include 6400 but not 8100 (one digit is odd) or 4248 (not a perfect square).

   781 \end{frame}

   782 

   783 \begin{frame}{Problem 2.4}

   784   The aliquot of a number is defined as: the sum of the \emph{proper} divisors of the number. For example, the aliquot(12) = 1 + 2 + 3 + 4 + 6 = 16.\\

   785   Write a function that returns the aliquot number of a given number. 

   786 \end{frame}

   787 

   788 \begin{frame}{Problem 2.5}

   789   A pair of numbers (a, b) is said to be \alert{amicable} if the aliquot number of a is b and the aliquot number of b is a.\\

   790   Example: \texttt{220, 284}\\

   791   Write a program that prints all five digit amicable pairs.

   792   \inctime{30}

   793 \end{frame}

   794 

   795 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   796 % TIME: 30 m, running 150m 

   797 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   798 

   799 \subsection{Lists}

   800 

   801 \begin{frame}[fragile]

   802   \frametitle{List creation and indexing}

   803 \begin{lstlisting}

   804 >>> a = [] # An empty list.

   805 >>> a = [1, 2, 3, 4] # More useful.

   806 >>> len(a) 

   807 4

   808 >>> a[0] + a[1] + a[2] + a[-1]

   809 10

   810 \end{lstlisting}

   811   \begin{itemize}

   812   \item Indices start with ?

   813   \item Negative indices indicate ?

   814   \end{itemize}

   815 \end{frame}

   816 

   817 \begin{frame}[fragile]

   818   \frametitle{List: slices}

   819   \begin{itemize}

   820   \item Slicing is a basic operation

   821   \item \typ{list[initial:final:step]}

   822   \item  The step is optional

   823   \end{itemize}

   824 \begin{lstlisting}

   825 >>> a[1:3] # A slice.

   826 [2, 3]

   827 >>> a[1:-1]

   828 [2, 3, 4]

   829 >>> a[1:] == a[1:-1]

   830 False  

   831 \end{lstlisting}

   832 Explain last result

   833 \end{frame}

   834 

   835 \begin{frame}[fragile]

   836   \frametitle{List: more slices}

   837 \begin{lstlisting}

   838 >>> a[0:-1:2] # Notice the step!

   839 [1, 3]

   840 >>> a[::2]

   841 [1, 3]

   842 >>> a[-1::-1]

   843 \end{lstlisting}

   844 What do you think the last one will do?

   845   \emphbar{Note: Strings also use same indexing and slicing.}

   846 \end{frame}

   847 

   848 \begin{frame}[fragile]

   849   \frametitle{List: examples}

   850 \begin{lstlisting}

   851 >>> a = [1, 2, 3, 4]

   852 >>> a[:2]

   853 [1, 3]

   854 >>> a[0:-1:2]

   855 [1, 3]

   856 \end{lstlisting}

   857 \pause

   858 \alert{Lists are mutable (unlike strings)}

   859 \begin{lstlisting}

   860 >>> a[1] = 20

   861 >>> a

   862 [1, 20, 3, 4]

   863 \end{lstlisting}

   864 \end{frame}

   865 

   866 \begin{frame}[fragile]

   867   \frametitle{Lists are mutable and heterogenous}

   868 \begin{lstlisting}

   869 >>> a = ['spam', 'eggs', 100, 1234]

   870 >>> a[2] = a[2] + 23

   871 >>> a

   872 ['spam', 'eggs', 123, 1234]

   873 >>> a[0:2] = [1, 12] # Replace items

   874 >>> a

   875 [1, 12, 123, 1234]

   876 >>> a[0:2] = [] # Remove items

   877 >>> a.append( 12345 )

   878 >>> a

   879 [123, 1234, 12345]

   880 \end{lstlisting}

   881 \end{frame}

   882 

   883 \begin{frame}[fragile]

   884   \frametitle{List methods}

   885 \begin{lstlisting}

   886 >>> a = ['spam', 'eggs', 1, 12]

   887 >>> a.reverse() # in situ

   888 >>> a

   889 [12, 1, 'eggs', 'spam']

   890 >>> a.append(['x', 1]) 

   891 >>> a

   892 [12, 1, 'eggs', 'spam', ['x', 1]]

   893 >>> a.extend([1,2]) # Extend the list.

   894 >>> a.remove( 'spam' )

   895 >>> a

   896 [12, 1, 'eggs', ['x', 1], 1, 2]

   897 \end{lstlisting}

   898 \end{frame}

   899 

   900 \begin{frame}[fragile]

   901   \frametitle{List containership}

   902   \begin{lstlisting}

   903 >>> a = ['cat', 'dog', 'rat', 'croc']

   904 >>> 'dog' in a

   905 True

   906 >>> 'snake' in a

   907 False

   908 >>> 'snake' not in a

   909 True

   910 >>> 'ell' in 'hello world'

   911 True

   912   \end{lstlisting}

   913 \end{frame}

   914 

   915 \begin{frame}[fragile]

   916   \frametitle{Tuples: immutable}

   917 \begin{lstlisting}

   918 >>> t = (0, 1, 2)

   919 >>> print t[0], t[1], t[2], t[-1] 

   920 0 1 2 2

   921 >>> t[0] = 1

   922 Traceback (most recent call last):

   923   File "<stdin>", line 1, in ?

   924 TypeError: object does not support item

   925            assignment

   926 \end{lstlisting}  

   927 \begin{itemize}

   928     \item Multiple return values are actually a tuple.

   929     \item Exchange is tuple (un)packing

   930 \end{itemize}

   931 

   932 \end{frame}

   933 

   934 \begin{frame}[fragile]

   935   \frametitle{\typ{range()} function}

   936   \begin{lstlisting}

   937 >>> range(7)

   938 [0, 1, 2, 3, 4, 5, 6]

   939 >>> range( 3, 9)

   940 [3, 4, 5, 6, 7, 8]

   941 >>> range( 4, 17, 3)

   942 [4, 7, 10, 13, 16]

   943 >>> range( 5, 1, -1)

   944 [5, 4, 3, 2]

   945 >>> range( 8, 12, -1)

   946 []

   947   \end{lstlisting}

   948 \end{frame}

   949 

   950 \begin{frame}[fragile]

   951   \frametitle{\typ{for\ldots range(\ldots)} idiom}

   952   \begin{lstlisting}

   953 In [83]: for i in range(5):

   954    ....:     print i, i * i

   955    ....:     

   956    ....:     

   957 0 0

   958 1 1

   959 2 4

   960 3 9

   961 4 16

   962 \end{lstlisting}

   963 \end{frame}

   964 

   965 \begin{frame}[fragile]

   966   \frametitle{\typ{for}: the list companion}

   967   

   968   \begin{lstlisting}

   969 In [84]: a = ['a', 'b', 'c']

   970 In [85]: for x in a:

   971    ....:    print x, chr( ord(x) + 10 )

   972    ....:

   973 a  k

   974 b  l

   975 c  m

   976   \end{lstlisting}

   977   Iterating over the list and not the index + reference\\

   978   what if you want the index?

   979 \end{frame}

   980 

   981 \begin{frame}[fragile]

   982   \frametitle{\typ{for}: the list companion}

   983   \begin{lstlisting}

   984 In [89]: for p, ch in enumerate( a ):

   985    ....:     print p, ch

   986    ....:     

   987    ....:     

   988 0 a

   989 1 b

   990 2 c

   991   \end{lstlisting}

   992 Try: \typ{print enumerate(a)}

   993 \inctime{20}

   994 \end{frame}

   995 

   996 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   997 % TIME: 20 m, running 170m 

   998 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   999 

  1000 \begin{frame}

  1001   {Problem set 3}

  1002   As you can guess, idea is to use \kwrd{for}!

  1003 \end{frame}

  1004 

  1005 \begin{frame}{Problem 3.1}

  1006   Which of the earlier problems is simpler when we use \kwrd{for} instead of \kwrd{while}? 

  1007 \end{frame}

  1008 

  1009 \begin{frame}{Problem 3.2}

  1010   Given an empty chessboard and one Bishop placed in any square, say (r, c), generate the list of all squares the Bishop could move to.

  1011 \end{frame}

  1012 

  1013 \begin{frame}[fragile]

  1014   \frametitle{Problem 3.3}

  1015 

  1016   Given two real numbers \typ{a, b}, and an integer \typ{N}, write a

  1017   function named \typ{linspace( a, b, N)} that returns an ordered list

  1018   of \typ{N} points starting with \typ{a} and ending in \typ{b} and

  1019   equally spaced.\\

  1020 

  1021   For example, \typ{linspace(0, 5, 11)}, should return, \\

  1022 \begin{lstlisting}

  1023 [ 0.0 ,  0.5,  1.0 ,  1.5,  2.0 ,  2.5,  

  1024   3.0 ,  3.5,  4.0 ,  4.5,  5.0 ]

  1025 \end{lstlisting}

  1026 \end{frame}

  1027 

  1028 \begin{frame}[fragile]

  1029   \frametitle{Problem 3.4a (optional)}

  1030 

  1031 Use the \typ{linspace} function and generate a list of N tuples of the form\\

  1032 \typ{[($x_1$,f($x_1$)),($x_2$,f($x_2$)),\ldots,($x_N$,f($x_N$))]}\\for the following functions,\begin{itemize}

  1033   \item \typ{f(x) = sin(x)}

  1034   \item \typ{f(x) = sin(x) + sin(10*x)}.

  1035 \end{itemize}

  1036 \end{frame}

  1037 

  1038 \begin{frame}[fragile]

  1039   \frametitle{Problem 3.4b (optional)}

  1040 

  1041   Using the tuples generated earlier, determine the intervals where the roots of the functions lie.

  1042 

  1043   \inctime{15}

  1044 \end{frame}

  1045 

  1046 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1047 % TIME: 15 m, running 185m 

  1048 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1049 

  1050 \subsection{IO}

  1051 

  1052 \begin{frame}[fragile]

  1053   \frametitle{Simple tokenizing and parsing}

  1054   \begin{lstlisting}

  1055 s = """The quick brown fox jumped

  1056        over the lazy dog"""

  1057 for word in s.split():

  1058     print word.capitalize()

  1059   \end{lstlisting}

  1060 \end{frame}

  1061 

  1062 \begin{frame}[fragile]

  1063   \frametitle{Problem 4.1}

  1064   Given a string like, ``1, 3-7, 12, 15, 18-21'', produce the list \\

  1065   \begin{lstlisting}

  1066     [1,3,4,5,6,7,12,15,18,19,20,21]

  1067   \end{lstlisting}

  1068 \end{frame}

  1069 

  1070 \begin{frame}[fragile]

  1071   \frametitle{File handling}

  1072 \begin{lstlisting}

  1073 >>> f = open('/path/to/file_name')

  1074 >>> data = f.read() # Read entire file.

  1075 >>> line = f.readline() # Read one line.

  1076 >>> f.close() # close the file.

  1077 \end{lstlisting}

  1078 Writing files

  1079 \begin{lstlisting}

  1080 >>> f = open('/path/to/file_name', 'w')

  1081 >>> f.write('hello world\n')

  1082 >>> f.close()

  1083 \end{lstlisting}

  1084 \begin{itemize}

  1085     \item Everything read or written is a string

  1086 \end{itemize}

  1087 \emphbar{Try \typ{file?} for more help}

  1088 \end{frame}

  1089 

  1090 \begin{frame}[fragile]

  1091     \frametitle{File and \kwrd{for}}

  1092 \begin{lstlisting}

  1093 >>> f = open('/path/to/file_name')

  1094 >>> for line in f:

  1095 ...     print line

  1096 ...

  1097 \end{lstlisting}

  1098 \end{frame}

  1099 

  1100 \begin{frame}{Problem 4.2}

  1101     The given file has lakhs of records in the form:\\

  1102     \typ{RGN;ID;NAME;MARK1;\ldots;MARK5;TOTAL;PFW}\\

  1103     Some entries may be empty.  Read the data from this file and print the

  1104     name of the student with the maximum total marks.

  1105 \end{frame}

  1106 

  1107 \begin{frame}{Problem 4.3}

  1108     For the same data file compute the average marks in different

  1109     subjects, the student with the maximum mark in each subject and also

  1110     the standard deviation of the marks.  Do this efficiently.

  1111 

  1112     \inctime{20}

  1113 \end{frame}

  1114 

  1115 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1116 % TIME: 20 m, running 205m 

  1117 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  1118 

  1119 \subsection{Modules}

  1120 

  1121 \begin{frame}[fragile]

  1122     {Modules}

  1123 \begin{lstlisting}

  1124 >>> sqrt(2)

  1125 Traceback (most recent call last):

  1126   File "<stdin>", line 1, in <module>

  1127 NameError: name 'sqrt' is not defined

  1128 >>> import math        

  1129 >>> math.sqrt(2)

  1130 1.4142135623730951

  1131 \end{lstlisting}

  1132 \end{frame}

  1133 

  1134 \begin{frame}[fragile]

  1135     {Modules}