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% Tutorial slides on Python.
%
% Author: Prabhu Ramachandran <prabhu at aero.iitb.ac.in>
% Copyright (c) 2005-2009, Prabhu Ramachandran
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% Title page
\title[Python Development]{Python Development}

\author[FOSSEE] {FOSSEE}

\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
\date[] {8 November, 2009\\Day 2, Session 4}
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\AtBeginSection[]
{
  \begin{frame}<beamer>
    \frametitle{Outline}
      \Large
    \tableofcontents[currentsection,currentsubsection]
  \end{frame}
}

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    \frametitle{Outline}
    \tableofcontents[currentsection,currentsubsection]
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    \frametitle{Outline}
    \tableofcontents[currentsection,currentsubsection]
  \end{frame}
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% DOCUMENT STARTS
\begin{document}

\begin{frame}
  \maketitle
\end{frame}

\section{Tests: Getting started}
\begin{frame}[fragile] 
  \frametitle{gcd revisited!}
  \begin{itemize}
  \item Open gcd.py
  \end{itemize}  
\begin{lstlisting}
    def gcd(a, b):
        if a % b == 0: 
            return b
        return gcd(b, a%b)

    print gcd(15, 65)
    print gcd(16, 76)
\end{lstlisting}
  \begin{itemize}
  \item python gcd.py
  \end{itemize}
\end{frame}

\begin{frame}[fragile] 
  \frametitle{Find lcm using our gcd module}
  \begin{itemize}
  \item Open lcm.py  
  \item $lcm = \frac{a*b}{gcd(a,b)}$
  \end{itemize}  
\begin{lstlisting}
    from gcd import gcd    
    def lcm(a, b):
        return (a * b) / gcd(a, b)
    
    print lcm(14, 56)
\end{lstlisting}
  \begin{itemize}
  \item python lcm.py
  \end{itemize}
  \begin{lstlisting}
5
4
56
  \end{lstlisting}    
\end{frame}

\begin{frame}[fragile] 
  \frametitle{Writing stand-alone module}  
Edit gcd.py file to:
\begin{lstlisting}
    def gcd(a, b):
        if a % b == 0: 
            return b
        return gcd(b, a%b)

    if __name__ == "__main__":        
        print gcd(15, 65)
        print gcd(16, 76)
\end{lstlisting}
  \begin{itemize}
  \item python gcd.py
  \item python lcm.py
  \end{itemize}
\end{frame}

\begin{frame}[fragile]
  \frametitle{More use of main}
  For automating tests.
  \begin{lstlisting}
if __name__ == '__main__':
    for line in open('numbers.txt'):
        numbers = line.split()
        x = int(numbers[0])
        y = int(numbers[1])
        result = (int(numbers[2]))
        assert gcd(x, y) == result
  \end{lstlisting}  
\end{frame}

\section{Coding Style}
\begin{frame}{Readability and Consistency}
    \begin{itemize}
        \item Readability Counts!\\Code is read more often than its written.
        \item Consistency!
        \item Know when to be inconsistent.
      \end{itemize}
\end{frame}

\begin{frame}[fragile] \frametitle{A question of good style}
  \begin{lstlisting}
    amount = 12.68
    denom = 0.05
    nCoins = round(amount/denom)
    rAmount = nCoins * denom
  \end{lstlisting}
  \pause
  \begin{block}{Style Rule \#1}
    Naming is 80\% of programming
  \end{block}
\end{frame}

\begin{frame}[fragile]
  \frametitle{Code Layout}
  \begin{itemize}
        \item Indentation
        \item Tabs or Spaces??
        \item Maximum Line Length
        \item Blank Lines
        \item Encodings
   \end{itemize}
\end{frame}

\begin{frame}{Whitespaces in Expressions}
  \begin{itemize}
        \item When to use extraneous whitespaces??
        \item When to avoid extra whitespaces??
        \item Use one statement per line
   \end{itemize}
\end{frame}

\begin{frame}{Comments}
  \begin{itemize}
        \item No comments better than contradicting comments
        \item Block comments
        \item Inline comments
   \end{itemize}
\end{frame}

\begin{frame}{Docstrings}
  \begin{itemize}
        \item When to write docstrings?
        \item Ending the docstrings
        \item One liner docstrings
   \end{itemize}
More information at PEP8: http://www.python.org/dev/peps/pep-0008/
\inctime{5}
\end{frame}

\section{Debugging}
\subsection{Errors and Exceptions}
\begin{frame}[fragile]
 \frametitle{Errors}
 \begin{lstlisting}
In []: 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}
In []: 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}
In []: 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}

\begin{frame}[fragile]
  \frametitle{Handling Exceptions}
  Python uses \typ{try} and \typ{except} clause.
  %%Revisiting the raw\_input
  \begin{lstlisting}
a = raw_input('Enter number(Q to quit):')
try:
    num = int(a)
    print num
except:
    if a == 'Q':
        print 'Exiting...'
    else:
        print 'Wrong input!'      
  \end{lstlisting}
  
  
\end{frame}

%% \begin{frame}[fragile]
%%   \frametitle{Solving it with \typ{try} and \typ{except}}
%% \vspace{-0.2in}
%%   \begin{lstlisting}
%% highest = 0
%% for record in open('sslc1.txt'):
%%     fields = record.split(';')
%%     try:
%%         total = 0
%%         for score_str in fields[3:8]:
%%             score = int(score_str)
%%             total += score
%%         if total > highest:
%%             highest = total
%%     except:        
%%         pass
%% print highest
%%   \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 []: import mymodule
In []: 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 []: %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}
science = {}

for record in open('sslc1.txt'):
    fields = record.split(';')
    region_code = fields[0].strip()

    score_str = fields[6].strip()
    score = int(score_str) if score_str != 'AA' 
                           else 0

    if score > 90:
        science[region_code] += 1

pie(science.values(), labels=science.keys())
savefig('science.png')
\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 for 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}    
def test_function_normal_words():
  input = "noon"
  assert is_palindrome(input) == True

if __name__ == "main'':
  test_function_normal_words()
\end{lstlisting}    
\end{frame}

\begin{frame}[fragile]
    \frametitle{Running the tests.}
\begin{lstlisting}    
$ nosetests palindrome.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 palindrome.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{Summary}
We have coverd:
  \begin{itemize}
  \item Following and Resolving Error Messages.
  \item Exceptions.
  \item Handling exceptions
  \item Approach for Debugging.
  \item Writting and running tests.
  \end{itemize}
\end{frame}

\end{document}