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% Tutorial slides on Python.

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

% Copyright (c) 2005-2009, Prabhu Ramachandran

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% Title page

\title[]{Debugging and \\Test Driven Approach}

\author[FOSSEE] {FOSSEE}

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

\date[] {11, October 2009}

\date[] % (optional)

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% DOCUMENT STARTS

\begin{document}

\begin{frame}

  \maketitle

\end{frame}

\section{Debugging}

\subsection{Errors and Exceptions}

\begin{frame}[fragile]

 \frametitle{Errors}

 \begin{lstlisting}

>>> while True print 'Hello world'

 \end{lstlisting}

\pause

  \begin{lstlisting}

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

    while True print 'Hello world'

                   ^

SyntaxError: invalid syntax

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

 \frametitle{Exceptions}

 \begin{lstlisting}

>>> print spam

\end{lstlisting}

\pause

\begin{lstlisting}

Traceback (most recent call last):

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

NameError: name 'spam' is not defined

\end{lstlisting}

\end{frame}

\begin{frame}[fragile]

 \frametitle{Exceptions}

 \begin{lstlisting}

>>> 1 / 0

\end{lstlisting}

\pause

\begin{lstlisting}

Traceback (most recent call last):

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

ZeroDivisionError: integer division 

or modulo by zero

\end{lstlisting}

\end{frame}

\subsection{Strategy}

\begin{frame}[fragile]

    \frametitle{Debugging effectively}

    \begin{itemize}

        \item \typ{print} based strategy

        \item Process:

    \end{itemize}

\begin{center}

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

\end{center}

\end{frame}

\begin{frame}[fragile]

    \frametitle{Debugging effectively}

    \begin{itemize}

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

    \end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Debugging in IPython}

\small

\begin{lstlisting}

In [1]: import mymodule

In [2]: mymodule.test()

---------------------------------------------

NameError   Traceback (most recent call last)

<ipython console> in <module>()

mymodule.py in test()

      1 def test():

----> 2     print spam

NameError: global name 'spam' is not defined

In [3]: %debug

> mymodule.py(2)test()

      0     print spam

ipdb> 

\end{lstlisting}

\inctime{15} 

\end{frame}

\subsection{Exercise}

\begin{frame}[fragile]

\frametitle{Debugging: Exercise}

\small

\begin{lstlisting}

import keyword

f = open('/path/to/file')

freq = {}

for line in f:

    words = line.split()

    for word in words:

        key = word.strip(',.!;?()[]: ')

        if keyword.iskeyword(key):

            value = freq[key]

            freq[key] = value + 1

print freq

\end{lstlisting}

\inctime{10}

\end{frame}

%% \begin{frame}

%%     \frametitle{Testing}

%%     \begin{itemize}

%%         \item Writing tests is really simple!

%%         \item Using nose.

%%         \item Example!

%%     \end{itemize}

%% \end{frame}

\section{Test Driven Approach}

\begin{frame}

    \frametitle{Need of Testing!}

    \begin{itemize}

        \item Quality

        \item Regression

        \item Documentation

    \end{itemize}

    %% \vspace*{0.25in}

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

\end{frame}

\begin{frame}[fragile]

    \frametitle{Example}

    \begin{block}{Problem Statement}

      Write a function to check whether a given input

      string is a palindrome.

    \end{block}

\end{frame}

\begin{frame}[fragile]

    \frametitle{Function: palindrome.py}

\begin{lstlisting}    

def is_palindrome(input_str):

  return input_str == input_str[::-1]

\end{lstlisting}    

\end{frame}

\begin{frame}[fragile]

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

\begin{lstlisting}    

from plaindrome import is_palindrome

def test_function_normal_words():

  input = "noon"

  assert is_palindrome(input) == True

\end{lstlisting}    

\end{frame}

\begin{frame}[fragile]

    \frametitle{Running the tests.}

\begin{lstlisting}    

$ nosetests test.py 

.

----------------------------------------------

Ran 1 test in 0.001s

OK

\end{lstlisting}    

\end{frame}

\begin{frame}[fragile]

    \frametitle{Exercise: Including new tests.}

\begin{lstlisting}    

def test_function_ignore_cases_words():

  input = "Noon"

  assert is_palindrome(input) == True

\end{lstlisting}

     \vspace*{0.25in}

     Check\\

     \PythonCode{$ nosetests test.py} \\

     \begin{block}{Task}

     Tweak the code to pass this test.

     \end{block}

\end{frame}

%\begin{frame}[fragile]

%    \frametitle{Lets write some test!}

%\begin{lstlisting}    

%#for form of equation y=mx+c

%#given m and c for two equation,

%#finding the intersection point.

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

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

%    y = m1*x+c1

%    return (x,y)

%\end{lstlisting}

%

%Create a simple test for this

%

%function which will make it fail.

%

%\inctime{15} 

%\end{frame}

%

\begin{frame}[fragile]

    \frametitle{Exercise}

    Based on Euclid's algorithm:

    \begin{center}

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

    \end{center}

    gcd function can be written as:

    \begin{lstlisting}

    def gcd(a, b):

      if a%b == 0: return b

      return gcd(b, a%b)

    \end{lstlisting}

    \vspace*{-0.15in}

    \begin{block}{Task}

      \begin{itemize}

      \item Write at least 

        two tests for above mentioned function.

      \item Write a non recursive implementation

      of gcd(), and test it using already 

      written tests.

      \end{itemize}

    \end{block}

\inctime{15} 

\end{frame}

\begin{frame}

  \frametitle{We have learned}

  \begin{itemize}

  \item Following and Resolving Error Messages.

  \item Exceptions.

  \item Approach for Debugging.

  \item Writting and running tests.

  \end{itemize}

\end{frame}

\end{document}