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    20 \usepackage{mathpazo,courier,euler} \usepackage[scaled=.95]{helvet}

    21 \usepackage{listings}

    22 \lstset{language=Python, basicstyle=\ttfamily\bfseries,

    23 commentstyle=\color{red}\itshape, stringstyle=\color{darkgreen},

    24 showstringspaces=false, keywordstyle=\color{blue}\bfseries}

    25 \providecommand{\alert}[1]{\textbf{#1}}

    26 

    27 \title{Getting started with functions}

    28 \author{FOSSEE}

    29 \date{}

    30 

    31 \usetheme{Warsaw}\usecolortheme{default}\useoutertheme{infolines}\setbeamercovered{transparent}

    32 \begin{document}

    33 

    34 \maketitle

    35 

    36 

    37 

    38 

    39 

    40 

    41 

    42 

    43 

    44     

    45     

    46 

    47 

    48 

    49 \begin{frame}

    50 \frametitle{Outline}

    51 \label{sec-1}

    52 

    53 \begin{itemize}

    54 \item Define functions

    55 \item Pass arguments to functions

    56 \item Learn about docstrings

    57 \item Return values from functions

    58 \end{itemize}

    59 \end{frame}

    60 \begin{frame}

    61 \frametitle{Function}

    62 \label{sec-2}

    63 

    64 \begin{itemize}

    65 \item Eliminate code redundancy

    66 \item Help in code reuse

    67 \item Subroutine

    68 

    69 \begin{itemize}

    70 \item relatively independent of remaining code

    71 \end{itemize}

    72 

    73 \end{itemize}

    74 \end{frame}

    75 \begin{frame}[fragile]

    76 \frametitle{\texttt{f(x)} a mathematical function}

    77 \label{sec-3}

    78 

    79 

    80   $f(x) = x^{2}$

    81 

    82 \begin{verbatim}

    83    f(1) -> 1

    84    f(2) -> 4

    85 \end{verbatim}

    86 \end{frame}

    87 \begin{frame}[fragile]

    88 \frametitle{Define \texttt{f(x)} in Python}

    89 \label{sec-4}

    90 

    91 \begin{verbatim}

    92 def f(x):

    93     return x*x

    94 \end{verbatim}

    95 

    96 \begin{itemize}

    97 \item \texttt{def} - keyword

    98 \item \texttt{f} - function name

    99 \item \texttt{x} - parameter / argument to function \texttt{f}

   100 \end{itemize}

   101 \end{frame}

   102 \begin{frame}

   103 \frametitle{Exercise 1}

   104 \label{sec-5}

   105 

   106 

   107   Write a python function named \texttt{cube} which computes the cube of a given

   108   number \texttt{n}.

   109   

   110 \begin{itemize}

   111 \item Pause here and try to solve the problem yourself.

   112 \end{itemize}

   113 \end{frame}

   114 \begin{frame}[fragile]

   115 \frametitle{Solution}

   116 \label{sec-6}

   117 

   118 \begin{verbatim}

   119 def cube(n):

   120     return n**3

   121 \end{verbatim}

   122 \end{frame}

   123 \begin{frame}[fragile]

   124 \frametitle{\texttt{greet} function}

   125 \label{sec-7}

   126 

   127 

   128  Function \texttt{greet} which will print \texttt{Hello World!}.

   129 \begin{verbatim}

   130 def greet():

   131     print "Hello World!"

   132 \end{verbatim}

   133 \begin{itemize}

   134 \item Call the function \texttt{greet}

   135 \begin{verbatim}

   136      In []: greet()

   137      Hello World!

   138 \end{verbatim}

   139 

   140 \end{itemize}

   141 \end{frame}

   142 \begin{frame}

   143 \frametitle{Exercise 2}

   144 \label{sec-8}

   145 

   146 

   147   Write a python function named \texttt{avg} which computes the average of

   148   \texttt{a} and \texttt{b}.

   149 

   150 \begin{itemize}

   151 \item Pause here and try to solve the problem yourself.

   152 \end{itemize}

   153 \end{frame}

   154 \begin{frame}[fragile]

   155 \frametitle{Solution 2}

   156 \label{sec-9}

   157 

   158 \begin{verbatim}

   159 def avg(a,b):

   160     return (a + b)/2

   161 \end{verbatim}

   162 

   163 \begin{itemize}

   164 \item \texttt{a} and \texttt{b} are parameters

   165 \item \texttt{def f(p1, p2, p3, ... , pn)}

   166 \end{itemize}

   167 \end{frame}

   168 \begin{frame}[fragile]

   169 \frametitle{Docstring}

   170 \label{sec-10}

   171 

   172 

   173 \begin{itemize}

   174 \item Documenting/commenting code is a good practice

   175 \begin{verbatim}

   176 def avg(a,b):

   177     """ avg takes two numbers as input 

   178     (a & b), and returns the average 

   179     of a and b"""

   180     return (a+b)/2

   181 \end{verbatim}

   182 \item Docstring

   183 

   184 \begin{itemize}

   185 \item written in the line after the \texttt{def} line.

   186 \item Inside triple quote.

   187 \end{itemize}

   188 

   189 \item Documentation

   190 \begin{verbatim}

   191      avg?

   192 \end{verbatim}

   193 

   194 \end{itemize}

   195 \end{frame}

   196 \begin{frame}

   197 \frametitle{Exercise 3}

   198 \label{sec-11}

   199 

   200   Add docstring to the function f.

   201 \end{frame}

   202 \begin{frame}[fragile]

   203 \frametitle{Solution 3}

   204 \label{sec-12}

   205 

   206 

   207 \begin{verbatim}

   208 def f(x):

   209     """Accepts a number x as argument and,

   210     returns the square of the number x."""

   211     return x*x

   212 \end{verbatim}

   213 \end{frame}

   214 \begin{frame}

   215 \frametitle{Exercise 4}

   216 \label{sec-13}

   217 

   218   Write a python function named \texttt{circle} which returns the area and

   219   perimeter of a circle given radius \texttt{r}.

   220 \end{frame}

   221 \begin{frame}[fragile]

   222 \frametitle{Solution 4}

   223 \label{sec-14}

   224 

   225 \begin{verbatim}

   226 def circle(r):

   227     """returns area and perimeter of a circle given 

   228     radius r"""

   229     pi = 3.14

   230     area = pi * r * r

   231     perimeter = 2 * pi * r

   232     return area, perimeter

   233 \end{verbatim}

   234 \end{frame}

   235 \begin{frame}[fragile]

   236 \frametitle{\texttt{what}}

   237 \label{sec-15}

   238 

   239 \begin{verbatim}

   240 

   241 def what( n ):

   242     if n < 0: n = -n

   243     while n > 0:

   244         if n % 2 == 1:

   245             return False

   246         n /= 10

   247     return True

   248 \end{verbatim}

   249 \end{frame}

   250 \begin{frame}[fragile]

   251 \frametitle{\texttt{even\_digits}}

   252 \label{sec-16}

   253 

   254 \begin{verbatim}

   255 def even_digits( n ):

   256    """returns True if all the digits of number 

   257    n is even returns False if all the digits 

   258    of number n is not even"""

   259     if n < 0: n = -n

   260     while n > 0:

   261         if n % 2 == 1:

   262             return False

   263         n /= 10

   264     return True

   265 \end{verbatim}

   266 \end{frame}

   267 \begin{frame}[fragile]

   268 \frametitle{\texttt{what}}

   269 \label{sec-17}

   270 

   271 \begin{verbatim}

   272 def what( n ):

   273     i = 1

   274     while i * i < n:

   275         i += 1

   276     return i * i == n, i

   277 \end{verbatim}

   278 \end{frame}

   279 \begin{frame}[fragile]

   280 \frametitle{\texttt{is\_perfect\_square}}

   281 \label{sec-18}

   282 

   283 \begin{verbatim}

   284 def is_perfect_square( n ):

   285     """returns True and square root of n, 

   286     if n is a perfect square, otherwise 

   287     returns False and the square root 

   288     of the next perfect square"""

   289     i = 1

   290     while i * i < n:

   291         i += 1

   292     return i * i == n, i

   293 \end{verbatim}

   294 \end{frame}

   295 \begin{frame}

   296 \frametitle{Summary}

   297 \label{sec-19}

   298 

   299 \begin{itemize}

   300 \item Functions in Python

   301 \item Passing parameters to a function

   302 \item Returning values from a function

   303 \item We also did few code reading exercises.

   304 \end{itemize}

   305 \end{frame}

   306 \begin{frame}

   307 \frametitle{Thank you!}

   308 \label{sec-20}

   309 

   310   \begin{block}{}

   311   \begin{center}

   312   This spoken tutorial has been produced by the

   313   \textcolor{blue}{FOSSEE} team, which is funded by the 

   314   \end{center}

   315   \begin{center}

   316     \textcolor{blue}{National Mission on Education through \\

   317       Information \& Communication Technology \\ 

   318       MHRD, Govt. of India}.

   319   \end{center}  

   320   \end{block}

   321 \end{frame}

   322 

   323 \end{document}