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

     2 % Tutorial slides on Python.

     3 %

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

     5 % Copyright (c) 2005-2009, Prabhu Ramachandran

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

     7 

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

     9 %\documentclass[draft]{beamer}

    10 %\documentclass[compress,handout]{beamer}

    11 %\usepackage{pgfpages} 

    12 %\pgfpagesuselayout{2 on 1}[a4paper,border shrink=5mm]

    13 

    14 % Modified from: generic-ornate-15min-45min.de.tex

    15 \mode<presentation>

    16 {

    17   \usetheme{Warsaw}

    18   \useoutertheme{split}

    19   \setbeamercovered{transparent}

    20 }

    21 

    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\bfseries,

    37     commentstyle=\color{red}\itshape,

    38   stringstyle=\color{darkgreen},

    39   showstringspaces=false,

    40   keywordstyle=\color{blue}\bfseries}

    41 

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

    43 % Macros

    44 \setbeamercolor{emphbar}{bg=blue!20, fg=black}

    45 \newcommand{\emphbar}[1]

    46 {\begin{beamercolorbox}[rounded=true]{emphbar} 

    47       {#1}

    48  \end{beamercolorbox}

    49 }

    50 \newcounter{time}

    51 \setcounter{time}{0}

    52 \newcommand{\inctime}[1]{\addtocounter{time}{#1}{\tiny \thetime\ m}}

    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:\\Functions and basic data structures}

    77 

    78 \author[FOSSEE Team] {Asokan Pichai\\Prabhu Ramachandran}

    79 

    80 \institute[FOSSEE] {FOSSEE Team}

    81 \date[] {10, October 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 

   113 \section{Python}

   114 

   115 \subsection{Exercises on Control flow}

   116 \begin{frame}

   117   \frametitle{Problem set 1}

   118   \begin{itemize}

   119     \item All the problems can be\\

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

   121   \end{itemize}

   122 \end{frame}

   123 

   124 \begin{frame}{Problem 1.1}

   125   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 $abc = a^3 + b^3 + c^3$\\

   126 These are called $Armstrong$ numbers.

   127 \end{frame}

   128   

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

   130 \begin{enumerate}

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

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

   133   \item Repeat the procedure with the new number.

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

   135 \end{enumerate}

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

   137 

   138 \end{frame}

   139 

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

   141   \begin{enumerate}

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

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

   144     \item Leave leading zeros in A!

   145     \item Subtract A from D.

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

   147   \end{enumerate}

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

   149 \end{frame}

   150 

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

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

   153   \begin{lstlisting}

   154 1

   155 2  2

   156 3  3  3

   157 4  4  4  4

   158   \end{lstlisting}

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

   160 \pause

   161 When can your code fail?

   162 \only<2->{\inctime{20}}

   163 \end{frame}

   164 

   165 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   166 % TIME: 20 m, running 20m 

   167 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   168 

   169 \subsection{Functions}

   170 \begin{frame}[fragile]

   171 \frametitle{Functions: examples}

   172   \begin{lstlisting}

   173 def signum( r ):

   174     """returns 0 if r is zero

   175     -1 if r is negative

   176     +1 if r is positive"""

   177     if r < 0:

   178         return -1

   179     elif r > 0:

   180         return 1

   181     else:

   182         return 0

   183   \end{lstlisting}

   184 \end{frame}

   185 

   186 \begin{frame}[fragile]

   187   \frametitle{Functions: examples}

   188   \begin{lstlisting}

   189 def pad( n, size ): 

   190     """pads integer n with spaces

   191     into a string of length size

   192     """

   193     SPACE = ' '

   194     s = str( n )

   195     padSize = size - len( s )

   196     return padSize * SPACE + s

   197   \end{lstlisting}

   198 \pause

   199 What about \%3d?

   200 \end{frame}

   201 

   202 \begin{frame}[fragile]

   203   {What does this function do?}

   204   \begin{lstlisting}

   205 def what( n ):

   206     if n < 0: n = -n

   207     while n > 0:

   208         if n % 2 == 1:

   209             return False

   210         n /= 10

   211     return True

   212   \end{lstlisting}

   213 \end{frame}

   214 

   215 \begin{frame}[fragile]

   216   {What does this function do?}

   217 \begin{lstlisting}

   218 def what( n ):

   219     i = 1    

   220     while i * i < n:

   221         i += 1

   222     return i * i == n, i

   223   \end{lstlisting}

   224 \end{frame}

   225 

   226 \begin{frame}[fragile]

   227   {What does this function do?}

   228   \begin{lstlisting}

   229 def what( n, x ):

   230     z = 1.0

   231     if n < 0:

   232         x = 1.0 / x

   233         n = -n

   234     while n > 0:

   235         if n % 2 == 1:

   236             z *= x

   237         n /= 2

   238         x *= x

   239     return z

   240   \end{lstlisting}

   241 \end{frame}

   242 

   243 \begin{frame}

   244   {Before writing a function}

   245   \begin{itemize}

   246       \item Builtin functions for various and sundry

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

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

   249       \item Refer here:

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

   251   \end{itemize}

   252   \inctime{10} 

   253 \end{frame}

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

   255 % TIME: 10 m, running 30m 

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

   257 

   258 \begin{frame}{Problem set 2}

   259   The focus is on writing functions and calling them.

   260 \end{frame}

   261 

   262 \begin{frame}{Problem 2.1}

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

   264 \end{frame}

   265 

   266 \begin{frame}{Problem 2.2}

   267 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. \\

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

   269 \end{frame}

   270 

   271 \begin{frame}{Problem 2.3}

   272   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).

   273 \end{frame}

   274 

   275 \begin{frame}{Problem 2.4}

   276   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.\\

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

   278 \end{frame}

   279 

   280 \begin{frame}{Problem 2.5}

   281   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.\\

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

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

   284   \inctime{25}

   285 \end{frame}

   286 

   287 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   288 % TIME: 25 m, running 55m 

   289 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   290 

   291 \subsection{Lists}

   292 

   293 \begin{frame}[fragile]

   294   \frametitle{List creation and indexing}

   295 \begin{lstlisting}

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

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

   298 >>> len(a) 

   299 4

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

   301 10

   302 \end{lstlisting}

   303   \begin{itemize}

   304   \item Indices start with ?

   305   \item Negative indices indicate ?

   306   \end{itemize}

   307 \end{frame}

   308 

   309 \begin{frame}[fragile]

   310   \frametitle{List: slices}

   311   \begin{itemize}

   312   \item Slicing is a basic operation

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

   314   \item  The step is optional

   315   \end{itemize}

   316 \begin{lstlisting}

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

   318 [2, 3]

   319 >>> a[1:-1]

   320 [2, 3]

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

   322 False  

   323 \end{lstlisting}

   324 Explain last result

   325 \end{frame}

   326 

   327 \begin{frame}[fragile]

   328   \frametitle{List: more slices}

   329 \begin{lstlisting}

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

   331 [1, 3]

   332 >>> a[::2]

   333 [1, 3]

   334 >>> a[-1::-1]

   335 \end{lstlisting}

   336 What do you think the last one will do?

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

   338 \end{frame}

   339 

   340 \begin{frame}[fragile]

   341   \frametitle{List: examples}

   342 \begin{lstlisting}

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

   344 >>> a[:2]

   345 [1, 2]

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

   347 [1, 3]

   348 \end{lstlisting}

   349 \pause

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

   351 \begin{lstlisting}

   352 >>> a[1] = 20

   353 >>> a

   354 [1, 20, 3, 4]

   355 \end{lstlisting}

   356 \end{frame}

   357 

   358 \begin{frame}[fragile]

   359   \frametitle{Lists are mutable and heterogenous}

   360 \begin{lstlisting}

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

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

   363 >>> a

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

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

   366 >>> a

   367 [1, 12, 123, 1234]

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

   369 >>> a.append( 12345 )

   370 >>> a

   371 [123, 1234, 12345]

   372 \end{lstlisting}

   373 \inctime{10}

   374 \end{frame}

   375 

   376 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   377 % TIME: 10 m, running 65m 

   378 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   379 

   380 \begin{frame}[fragile]

   381   \frametitle{List methods}

   382 \begin{lstlisting}

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

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

   385 >>> a

   386 [12, 1, 'eggs', 'spam']

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

   388 >>> a

   389 [12, 1, 'eggs', 'spam', ['x', 1]]

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

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

   392 >>> a

   393 [12, 1, 'eggs', ['x', 1], 1, 2]

   394 \end{lstlisting}

   395 \end{frame}

   396 

   397 \begin{frame}[fragile]

   398   \frametitle{List containership}

   399   \begin{lstlisting}

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

   401 >>> 'dog' in a

   402 True

   403 >>> 'snake' in a

   404 False

   405 >>> 'snake' not in a

   406 True

   407 >>> 'ell' in 'hello world'

   408 True

   409   \end{lstlisting}

   410   \inctime{5}

   411 \end{frame}

   412 

   413 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   414 % TIME: 5 m, running 70m 

   415 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   416 

   417 \begin{frame}[fragile]

   418   \frametitle{Tuples: immutable}

   419 \begin{lstlisting}

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

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

   422 0 1 2 2

   423 >>> t[0] = 1

   424 Traceback (most recent call last):

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

   426 TypeError: object does not support item assignment

   427 \end{lstlisting}  

   428 \begin{itemize}

   429     \item Multiple return values are actually a tuple.

   430     \item Exchange is tuple (un)packing

   431 \end{itemize}

   432 \inctime{5}

   433 \end{frame}

   434 

   435 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   436 % TIME: 5 m, running 75m 

   437 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   438 

   439 \begin{frame}[fragile]

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

   441   \begin{lstlisting}

   442 >>> range(7)

   443 [0, 1, 2, 3, 4, 5, 6]

   444 >>> range( 3, 9)

   445 [3, 4, 5, 6, 7, 8]

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

   447 [4, 7, 10, 13, 16]

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

   449 [5, 4, 3, 2]

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

   451 []

   452   \end{lstlisting}

   453 \end{frame}

   454 

   455 \begin{frame}[fragile]

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

   457   \begin{lstlisting}

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

   459    ....:     print i, i * i

   460    ....:     

   461    ....:     

   462 0 0

   463 1 1

   464 2 4

   465 3 9

   466 4 16

   467 \end{lstlisting}

   468 \end{frame}

   469 

   470 \begin{frame}[fragile]

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

   472   

   473   \begin{lstlisting}

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

   475 In [85]: for x in a:

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

   477    ....:

   478 a  k

   479 b  l

   480 c  m

   481   \end{lstlisting}

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

   483   what if you want the index?

   484 \end{frame}

   485 

   486 \begin{frame}[fragile]

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

   488   \begin{lstlisting}

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

   490    ....:     print p, ch

   491    ....:     

   492    ....:     

   493 0 a

   494 1 b

   495 2 c

   496   \end{lstlisting}

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

   498 \inctime{10}

   499 \end{frame}

   500 

   501 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   502 % TIME: 10 m, running 85m 

   503 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   504 

   505 \begin{frame}

   506   \frametitle{Did we meet the goal?}

   507   \tableofcontents

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

   509 \end{frame}

   510 

   511 \end{document}