1 \documentclass[12pt]{article}

     2 

     3 

     4 \title{Python: Data Structures}

     5 \author{FOSSEE}

     6 \usepackage{listings}

     7 \lstset{language=Python,

     8     basicstyle=\ttfamily,

     9 commentstyle=\itshape\bfseries, 

    10 showstringspaces=false

    11 }

    12 \newcommand{\typ}[1]{\lstinline{#1}}

    13 \usepackage[english]{babel}

    14 \usepackage[latin1]{inputenc}

    15 \usepackage{times}

    16 \usepackage[T1]{fontenc}

    17 \usepackage{ae,aecompl}

    18 \usepackage{mathpazo,courier,euler}

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

    20 

    21 \begin{document}

    22 \date{}

    23 \vspace{-1in}

    24 \begin{center}

    25 \LARGE{Python: Python Development}\\

    26 \large{FOSSEE}

    27 \end{center}

    28 \section{Module}

    29 Packages like \typ{scipy}, \typ{pylab} etc we used for functions like \typ{plot} are Modules. Modules are Python script, which have various functions and objects, which if imported can be reused. 

    30 \begin{lstlisting}

    31 def gcd(a, b):

    32   if a % b == 0: 

    33     return b

    34   return gcd(b, a%b)

    35 

    36 print gcd(15, 65)

    37 print gcd(16, 76)

    38 \end{lstlisting}

    39 Save above mentioned python script with name 'gcd.py'. Now we can \typ{import} \typ{gcd} function. For example, in same directory create 'lcm.py' with following content:

    40 \begin{lstlisting}

    41 from gcd import gcd    

    42 def lcm(a, b):

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

    44     

    45 print lcm(14, 56)

    46 \end{lstlisting}

    47 Here since both gcd.py and lcm.py are in same directory, import statement imports \typ{gcd} function from gcd.py.\\

    48 When you try to run lcm.py it prints three results, two from gcd.py and third from lcm.py.

    49 \begin{lstlisting}

    50 $ python lcm.py

    51 5

    52 4

    53 56

    54 \end{lstlisting} %$

    55 \newpage

    56 We have print statements to make sure \typ{gcd} and \typ{lcm} are working properly. So to suppress output of \typ{gcd} module when imported in lcm.py we use \typ{'__main__'} \

    57 \begin{lstlisting}

    58 def gcd(a, b):

    59   if a % b == 0: 

    60     return b

    61   return gcd(b, a%b)

    62 if __name__ == '__main__':

    63   print gcd(15, 65)

    64   print gcd(16, 76)

    65 \end{lstlisting}

    66 This \typ{__main__()} helps to create standalone scripts. Code inside it is only executed when we run gcd.py. Hence

    67 \begin{lstlisting}

    68 $ python gcd.py

    69 5

    70 4

    71 $ python lcm.py 

    72 56

    73 \end{lstlisting}

    74 \end{document}