2 %Tutorial slides on Python.

     2 % Tutorial slides on Python.

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    24 %\usepackage{times}

    38 \usepackage{times}

    43 % Macros

    58 % My Macros

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    80 \newcommand{\inctime}[1]{\addtocounter{time}{#1}{\vspace*{0.1in}\tiny \thetime\ m}}

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

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    59 % \usepackage{color}

    87 }}}

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

    88 

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

    89 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    62 % \usepackage{listings}

    90 % Configuring the theme

    63 % \lstset{

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    68 %    showstringspaces=false,

    69 %    breaklines=true,

    70 %    postbreak = \space\dots

    71 % }

    76 \title[Exercises]{Exercises}

    98 \title[Python Development]{Python Development}

    81 \date[] {1 November, 2009\\Day 2, Session 4}

   103 \date[] {1 November, 2009\\Day 2, Session 3}

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

   106 %\pgfdeclareimage[height=0.75cm]{iitblogo}{iitblogo}

    85 %\logo{\pgfuseimage{iitmlogo}}

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    86 

   108 

   109 \AtBeginSection[]

   110 {

   111   \begin{frame}<beamer>

   112     \frametitle{Outline}

   113       \Large

   114     \tableofcontents[currentsection,currentsubsection]

   115   \end{frame}

   116 }

    98 

   128 \AtBeginSection[]

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

   129 {

   100 % the following command: 

   130   \begin{frame}<beamer>

   101 %\beamerdefaultoverlayspecification{<+->}

   131     \frametitle{Outline}

   102 

   132     \tableofcontents[currentsection,currentsubsection]

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

   133   \end{frame}

   104 

   134 }

   110   \titlepage

   140   \maketitle

   111 \end{frame}

   141 \end{frame}

   112 

   142 

   113 \begin{frame}{Problem 1.1}

   143 \section{Tests: Getting started}

   114   The aliquot of a number is defined as: the sum of the \emph{proper} divisors of the number. \\For example: 

   144 \begin{frame}[fragile] 

   115 \center{aliquot(12) = 1 + 2 + 3 + 4 + 6 = 16.}\\

   145   \frametitle{gcd revisited!}

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

   146   \begin{itemize}

   117 \end{frame}

   147   \item Open gcd.py

   118 

   148   \end{itemize}  

   119 \begin{frame}{Problem 1.2}

   149 \begin{lstlisting}

   120   Pair of numbers (a, b) is said to be \alert{amicable} if aliquot number of a is b and aliquot number of b is a.\\

   150     def gcd(a, b):

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

   151         if a % b == 0: 

   122   Write a program that prints all four digit amicable pairs.

   152             return b

   123   

   153         return gcd(b, a%b)

   124 \inctime{20}

   154 

   125 \end{frame}

   155     print gcd(15, 65)

   126 

   156     print gcd(16, 76)

   127 %% \begin{frame}{Problem 2}

   157 \end{lstlisting}

   128 %%   Given an empty chessboard and one Bishop placed in any s%quare, say (r, c), generate the list of all squares the Bi%shop could move to.

   158   \begin{itemize}

   129 

   159   \item python gcd.py

   130 %% \end{frame}

   160   \end{itemize}

   131 

   161 \end{frame}

   132 \begin{frame}[fragile]

   162 

   133   \frametitle{Problem Set 2}

   163 \begin{frame}[fragile] 

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

   164   \frametitle{Find lcm using our gcd module}

   165   \begin{itemize}

   166   \item Open lcm.py  

   167   \item $lcm = \frac{a*b}{gcd(a,b)}$

   168   \end{itemize}  

   169 \begin{lstlisting}

   170     from gcd import gcd    

   171     def lcm(a, b):

   172         return (a * b) / gcd(a, b)

   173     

   174     print lcm(14, 56)

   175 \end{lstlisting}

   176   \begin{itemize}

   177   \item python lcm.py

   178   \end{itemize}

   136     [1,3,4,5,6,7,12,15,18,19,20,21]

   180 5

   137   \end{lstlisting}

   181 4

   138 \inctime{10}

   182 56

   139 \end{frame}

   183   \end{lstlisting}    

   140 

   184 \end{frame}

   141 \begin{frame} 

   185 

   142   \frametitle{Problem Set 3}

   186 \begin{frame}[fragile] 

   143   \begin{description}

   187   \frametitle{Writing stand-alone module}  

   144     \item[3.1] Count word frequencies in a file.

   188 Edit gcd.py file to:

   145 \end{description}

   189 \begin{lstlisting}

   146 \inctime{5}

   190     def gcd(a, b):

   147 \end{frame}

   191         if a % b == 0: 

   148 

   192             return b

   149 \begin{frame}[fragile]

   193         return gcd(b, a%b)

   150   \frametitle{Problem set 4}

   194 

   151   Central difference

   195     if __name__ == "__main__":        

   152   \begin{equation*}

   196         print gcd(15, 65)

   153   \frac{sin(x+h)-sin(x-h)}{2h}

   197         print gcd(16, 76)

   154   \end{equation*}

   198 \end{lstlisting}

   199   \begin{itemize}

   200   \item python gcd.py

   201   \item python lcm.py

   202   \end{itemize}

   203 \end{frame}

   204 

   205 \begin{frame}[fragile]

   206   \frametitle{More use of main}

   207   For automating tests.

   156   In []: x = linspace(0, 2*pi, 100)

   209 if __name__ == '__main__':

   157   In []: y = sin(x)

   210     for line in open('numbers.txt'):

   158   In []: deltax = x[1] - x[0]

   211         numbers = line.split()

   212         x = int(numbers[0])

   213         y = int(numbers[1])

   214         result = (int(numbers[2]))

   215         assert gcd(x, y) == result

   216   \end{lstlisting}  

   217 \end{frame}

   218 

   219 \section{Coding Style}

   220 \begin{frame}{Readability and Consistency}

   221     \begin{itemize}

   222         \item Readability Counts!\\Code is read more often than its written.

   223         \item Consistency!

   224         \item Know when to be inconsistent.

   225       \end{itemize}

   226 \end{frame}

   227 

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

   229   \begin{lstlisting}

   230     amount = 12.68

   231     denom = 0.05

   232     nCoins = round(amount/denom)

   233     rAmount = nCoins * denom

   161     \begin{enumerate}

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

   162       \item Given this, get the finite difference of sin in the range 0 to 2*pi

   237     Naming is 80\% of programming

   163     \end{enumerate}

   238   \end{block}

   164 \end{frame}

   239 \end{frame}

   165 

   240 

   241 \begin{frame}[fragile]

   242   \frametitle{Code Layout}

   243   \begin{itemize}

   244         \item Indentation

   245         \item Tabs or Spaces??

   246         \item Maximum Line Length

   247         \item Blank Lines

   248         \item Encodings

   249    \end{itemize}

   250 \end{frame}

   251 

   252 \begin{frame}{Whitespaces in Expressions}

   253   \begin{itemize}

   254         \item When to use extraneous whitespaces??

   255         \item When to avoid extra whitespaces??

   256         \item Use one statement per line

   257    \end{itemize}

   258 \end{frame}

   259 

   260 \begin{frame}{Comments}

   261   \begin{itemize}

   262         \item No comments better than contradicting comments

   263         \item Block comments

   264         \item Inline comments

   265    \end{itemize}

   266 \end{frame}

   267 

   268 \begin{frame}{Docstrings}

   269   \begin{itemize}

   270         \item When to write docstrings?

   271         \item Ending the docstrings

   272         \item One liner docstrings

   273    \end{itemize}

   274 More information at PEP8: http://www.python.org/dev/peps/pep-0008/

   275 \inctime{5}

   276 \end{frame}

   277 

   278 \section{Debugging}

   279 \subsection{Errors and Exceptions}

   280 \begin{frame}[fragile]

   281  \frametitle{Errors}

   282  \begin{lstlisting}

   283 In []: while True print 'Hello world'

   284  \end{lstlisting}

   285 \pause

   286   \begin{lstlisting}

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

   288     while True print 'Hello world'

   289                    ^

   290 SyntaxError: invalid syntax

   291 \end{lstlisting}

   292 \end{frame}

   293 

   294 \begin{frame}[fragile]

   295  \frametitle{Exceptions}

   296  \begin{lstlisting}

   297 In []: print spam

   298 \end{lstlisting}

   299 \pause

   300 \begin{lstlisting}

   301 Traceback (most recent call last):

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

   303 NameError: name 'spam' is not defined

   304 \end{lstlisting}

   305 \end{frame}

   306 

   307 \begin{frame}[fragile]

   308  \frametitle{Exceptions}

   309  \begin{lstlisting}

   310 In []: 1 / 0

   311 \end{lstlisting}

   312 \pause

   313 \begin{lstlisting}

   314 Traceback (most recent call last):

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

   316 ZeroDivisionError: integer division 

   317 or modulo by zero

   318 \end{lstlisting}

   319 \end{frame}

   320 

   321 \begin{frame}[fragile]

   322   \frametitle{Handling Exceptions}

   323   Python uses \typ{try} and \typ{except} clause.

   324   %%Revisiting the raw\_input

   325   \begin{lstlisting}

   326 a = raw_input('Enter number(Q to quit):')

   327 try:

   328     num = int(a)

   329     print num

   330 except:

   331     if a == 'Q':

   332         print 'Exiting...'

   333     else:

   334         print 'Wrong input!'      

   335   \end{lstlisting}

   336   

   337   

   338 \end{frame}

   339 

   340 %% \begin{frame}[fragile]

   341 %%   \frametitle{Solving it with \typ{try} and \typ{except}}

   342 %% \vspace{-0.2in}

   343 %%   \begin{lstlisting}

   344 %% highest = 0

   345 %% for record in open('sslc1.txt'):

   346 %%     fields = record.split(';')

   347 %%     try:

   348 %%         total = 0

   349 %%         for score_str in fields[3:8]:

   350 %%             score = int(score_str)

   351 %%             total += score

   352 %%         if total > highest:

   353 %%             highest = total

   354 %%     except:        

   355 %%         pass

   356 %% print highest

   357 %%   \end{lstlisting}

   358 %% \end{frame}

   359 \subsection{Strategy}

   360 \begin{frame}[fragile]

   361     \frametitle{Debugging effectively}

   362     \begin{itemize}

   363         \item \typ{print} based strategy

   364         \item Process:

   365     \end{itemize}

   366 \begin{center}

   367 \pgfimage[interpolate=true,width=5cm,height=5cm]{DebugginDiagram.png}

   368 \end{center}

   369 \end{frame}

   370 

   371 \begin{frame}[fragile]

   372     \frametitle{Debugging effectively}

   373     \begin{itemize}

   374       \item Using \typ{\%debug} in IPython

   375     \end{itemize}

   376 \end{frame}

   377 

   378 \begin{frame}[fragile]

   379 \frametitle{Debugging in IPython}

   380 \small

   381 \begin{lstlisting}

   382 In []: import mymodule

   383 In []: mymodule.test()

   384 ---------------------------------------------

   385 NameError   Traceback (most recent call last)

   386 <ipython console> in <module>()

   387 mymodule.py in test()

   388       1 def test():

   389 ----> 2     print spam

   390 NameError: global name 'spam' is not defined

   391 

   392 In []: %debug

   393 > mymodule.py(2)test()

   394       0     print spam

   395 ipdb> 

   396 \end{lstlisting}

   397 \inctime{15} 

   398 \end{frame}

   399 

   400 \subsection{Exercise}

   401 \begin{frame}[fragile]

   402 \frametitle{Debugging: Exercise}

   403 \small

   404 \begin{lstlisting}

   405 science = {}

   406 

   407 for record in open('sslc1.txt'):

   408     fields = record.split(';')

   409     region_code = fields[0].strip()

   410 

   411     score_str = fields[6].strip()

   412     score = int(score_str) if score_str != 'AA' 

   413                            else 0

   414 

   415     if score > 90:

   416         science[region_code] += 1

   417 

   418 pie(science.values(), labels=science.keys())

   419 savefig('science.png')

   420 \end{lstlisting}

   421 \inctime{10}

   422 \end{frame}

   423 

   424 %% \begin{frame}

   425 %%     \frametitle{Testing}

   426    

   427 %%     \begin{itemize}

   428 %%         \item Writing tests is really simple!

   429 

   430 %%         \item Using nose.

   431 

   432 %%         \item Example!

   433 %%     \end{itemize}

   434 %% \end{frame}

   435 

   436 \section{Test Driven Approach}

   167   \frametitle{Problem Set 5}

   438     \frametitle{Need for Testing!}

   168   \begin{itemize}

   439    

   169       \item[5.1] Write a function that plots any regular n-gon given \typ{n}.

   170       \item[5.2] Consider the logistic map, $f(x) = kx(1-x)$, plot it for

   171           $k=2.5, 3.5$ and $4$ in the same plot.

   172 \end{itemize}

   173 \end{frame}

   174 

   175 \begin{frame}[fragile] 

   176 \frametitle{Problem Set 5}

   177   \begin{columns}

   178     \column{0.6\textwidth}

   179     \small{

   181       \item[3] Consider the iteration $x_{n+1} = f(x_n)$ where $f(x) = kx(1-x)$.  Plot the successive iterates of this process as explained below. 

   441         \item Quality

   182     \end{itemize}}

   442         \item Regression

   183     \column{0.35\textwidth}

   443         \item Documentation

   184     \hspace*{-0.5in}

   444     \end{itemize}

   185   \includegraphics[height=1.6in, interpolate=true]{data/cobweb}  

   445     %% \vspace*{0.25in}

   186 \end{columns}

   446     %% \emphbar{It is to assure that section of code is working as it is supposed to work}

   187 \end{frame}

   447 \end{frame}

   448 

   449 \begin{frame}[fragile]

   450     \frametitle{Example}

   451     \begin{block}{Problem Statement}

   452       Write a function to check whether a given input

   453       string is a palindrome.

   454     \end{block}

   455 \end{frame}

   456 

   457 \begin{frame}[fragile]

   458     \frametitle{Function: palindrome.py}

   459 \begin{lstlisting}    

   460 def is_palindrome(input_str):

   461   return input_str == input_str[::-1]

   462 \end{lstlisting}    

   463 \end{frame}

   464 

   465 \begin{frame}[fragile]

   466     \frametitle{Test for the palindrome: palindrome.py}

   467 \begin{lstlisting}    

   468 def test_function_normal_words():

   469   input = "noon"

   470   assert is_palindrome(input) == True

   471 

   472 if __name__ == "main'':

   473   test_function_normal_words()

   474 \end{lstlisting}    

   475 \end{frame}

   476 

   477 \begin{frame}[fragile]

   478     \frametitle{Running the tests.}

   479 \begin{lstlisting}    

   480 $ nosetests palindrome.py 

   481 .

   482 ----------------------------------------------

   483 Ran 1 test in 0.001s

   484 

   485 OK

   486 \end{lstlisting}    

   487 \end{frame}

   488 

   489 \begin{frame}[fragile]

   490     \frametitle{Exercise: Including new tests.}

   491 \begin{lstlisting}    

   492 def test_function_ignore_cases_words():

   493   input = "Noon"

   494   assert is_palindrome(input) == True

   495 \end{lstlisting}

   496      \vspace*{0.25in}

   497      Check\\

   498      \PythonCode{$ nosetests palindrome.py} \\

   499      \begin{block}{Task}

   500      Tweak the code to pass this test.

   501      \end{block}

   502 \end{frame}

   503 

   504 %\begin{frame}[fragile]

   505 %    \frametitle{Lets write some test!}

   506 %\begin{lstlisting}    

   507 %#for form of equation y=mx+c

   508 %#given m and c for two equation,

   509 %#finding the intersection point.

   510 %def intersect(m1,c1,m2,c2):

   511 %    x = (c2-c1)/(m1-m2)

   512 %    y = m1*x+c1

   513 %    return (x,y)

   514 %\end{lstlisting}

   515 %

   516 %Create a simple test for this

   517 %

   518 %function which will make it fail.

   519 %

   520 %\inctime{15} 

   521 %\end{frame}

   522 %

   523 

   524 %% \begin{frame}[fragile]

   525 %%     \frametitle{Exercise}

   526 %%     Based on Euclid's algorithm:

   527 %%     \begin{center}

   528 %%     $gcd(a,b)=gcd(b,b\%a)$

   529 %%     \end{center}

   530 %%     gcd function can be written as:

   531 %%     \begin{lstlisting}

   532 %%     def gcd(a, b):

   533 %%       if a%b == 0: return b

   534 %%       return gcd(b, a%b)

   535 %%     \end{lstlisting}

   536 %%     \vspace*{-0.15in}

   537 %%     \begin{block}{Task}

   538 %%       \begin{itemize}

   539 %%       \item Write at least 

   540 %%         two tests for above mentioned function.

   541 %%       \item Write a non recursive implementation

   542 %%       of gcd(), and test it using already 

   543 %%       written tests.

   544 %%       \end{itemize}

   545 %%     \end{block}

   546     

   547 %% \inctime{15} 

   548 %% \end{frame}

   190   \frametitle{Problem Set 5.3}

   551   \frametitle{Summary}

   191   Plot the cobweb plot as follows:

   552 We have coverd:

   192   \begin{enumerate}

   553   \begin{itemize}

   193     \item Start at $(x_0, 0)$ ($\implies$ i=0)

   554   \item Following and Resolving Error Messages.

   194     \item Draw a line to $(x_i, f(x_i))$

   555   \item Exceptions.

   195     \item Set $x_{i+1} = f(x_i)$

   556   \item Handling exceptions

   196     \item Draw a line to $(x_{i+1}, x_{i+1})$

   557   \item Approach for Debugging.

   197     \item $(i\implies i+1)$ 

   558   \item Writting and running tests.

   198     \item Repeat from 2 for as long as you want 

   559   \end{itemize}

   199   \end{enumerate}

   200 \inctime{20}