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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 \begin{frame}

    45 \frametitle{Outline}

    46 \label{sec-1}

    47 

    48 \begin{itemize}

    49 \item Define functions

    50 \item Pass arguments to functions

    51 \item Learn about docstrings

    52 \item Return values from functions

    53 \end{itemize}

    54 \end{frame}

    55 \begin{frame}

    56 \frametitle{Function}

    57 \label{sec-2}

    58 

    59 \begin{itemize}

    60 \item Eliminate code redundancy

    61 \item Help in code reuse

    62 \item Subroutine

    63 

    64 \begin{itemize}

    65 \item relatively independent of remaining code

    66 \end{itemize}

    67 

    68 \end{itemize}

    69 \end{frame}

    70 \begin{frame}[fragile]

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

    72 \label{sec-3}

    73 

    74 

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

    76 

    77 \begin{verbatim}

    78    f(1) -> 1

    79    f(2) -> 4

    80 \end{verbatim}

    81 \end{frame}

    82 \begin{frame}[fragile]

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

    84 \label{sec-4}

    85 

    86 \begin{verbatim}

    87 def f(x):

    88     return x*x

    89 \end{verbatim}

    90 

    91 \begin{itemize}

    92 \item \texttt{def} - keyword

    93 \item \texttt{f} - function name

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

    95 \end{itemize}

    96 \end{frame}

    97 \begin{frame}

    98 \frametitle{Exercise 1}

    99 \label{sec-5}

   100 

   101 

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

   103   number \texttt{n}.

   104   

   105 \begin{itemize}

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

   107 \end{itemize}

   108 \end{frame}

   109 \begin{frame}[fragile]

   110 \frametitle{Solution}

   111 \label{sec-6}

   112 

   113 \begin{verbatim}

   114 def cube(n):

   115     return n**3

   116 \end{verbatim}

   117 \end{frame}

   118 \begin{frame}[fragile]

   119 \frametitle{\texttt{greet} function}

   120 \label{sec-7}

   121 

   122 

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

   124 \begin{verbatim}

   125 def greet():

   126     print "Hello World!"

   127 \end{verbatim}

   128 \begin{itemize}

   129 \item Call the function \texttt{greet}

   130 \begin{verbatim}

   131      In []: greet()

   132      Hello World!

   133 \end{verbatim}

   134 

   135 \end{itemize}

   136 \end{frame}

   137 \begin{frame}

   138 \frametitle{Exercise 2}

   139 \label{sec-8}

   140 

   141 

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

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

   144 

   145 \begin{itemize}

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

   147 \end{itemize}

   148 \end{frame}

   149 \begin{frame}[fragile]

   150 \frametitle{Solution 2}

   151 \label{sec-9}

   152 

   153 \begin{verbatim}

   154 def avg(a,b):

   155     return (a + b)/2

   156 \end{verbatim}

   157 

   158 \begin{itemize}

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

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

   161 \end{itemize}

   162 \end{frame}

   163 \begin{frame}[fragile]

   164 \frametitle{Docstring}

   165 \label{sec-10}

   166 

   167 

   168 \begin{itemize}

   169 \item Documenting/commenting code is a good practice

   170 \begin{verbatim}

   171 def avg(a,b):

   172     """ avg takes two numbers as input 

   173     (a & b), and returns the average 

   174     of a and b"""

   175     return (a+b)/2

   176 \end{verbatim}

   177 \item Docstring

   178 

   179 \begin{itemize}

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

   181 \item Inside triple quote.

   182 \end{itemize}

   183 

   184 \item Documentation

   185 \begin{verbatim}

   186      avg?

   187 \end{verbatim}

   188 

   189 \end{itemize}

   190 \end{frame}

   191 \begin{frame}

   192 \frametitle{Exercise 3}

   193 \label{sec-11}

   194 

   195   Add docstring to the function f.

   196 \end{frame}

   197 \begin{frame}[fragile]

   198 \frametitle{Solution 3}

   199 \label{sec-12}

   200 

   201 

   202 \begin{verbatim}

   203 def f(x):

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

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

   206     return x*x

   207 \end{verbatim}

   208 \end{frame}

   209 \begin{frame}

   210 \frametitle{Exercise 4}

   211 \label{sec-13}

   212 

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

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

   215 \end{frame}

   216 \begin{frame}[fragile]

   217 \frametitle{Solution 4}

   218 \label{sec-14}

   219 

   220 \begin{verbatim}

   221 def circle(r):

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

   223     radius r"""

   224     pi = 3.14

   225     area = pi * r * r

   226     perimeter = 2 * pi * r

   227     return area, perimeter

   228 \end{verbatim}

   229 \end{frame}

   230 \begin{frame}[fragile]

   231 \frametitle{\texttt{what}}

   232 \label{sec-15}

   233 

   234 \begin{verbatim}

   235 

   236 def what( n ):

   237     if n < 0: n = -n

   238     while n > 0:

   239         if n % 2 == 1:

   240             return False

   241         n /= 10

   242     return True

   243 \end{verbatim}

   244 \end{frame}

   245 \begin{frame}[fragile]

   246 \frametitle{\texttt{even\_digits}}

   247 \label{sec-16}

   248 

   249 \begin{verbatim}

   250 def even_digits( n ):

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

   252    n is even returns False if all the digits 

   253    of number n is not even"""

   254     if n < 0: n = -n

   255     while n > 0:

   256         if n % 2 == 1:

   257             return False

   258         n /= 10

   259     return True

   260 \end{verbatim}

   261 \end{frame}

   262 \begin{frame}[fragile]

   263 \frametitle{\texttt{what}}

   264 \label{sec-17}

   265 

   266 \begin{verbatim}

   267 def what( n ):

   268     i = 1

   269     while i * i < n:

   270         i += 1

   271     return i * i == n, i

   272 \end{verbatim}

   273 \end{frame}

   274 \begin{frame}[fragile]

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

   276 \label{sec-18}

   277 

   278 \begin{verbatim}

   279 def is_perfect_square( n ):

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

   281     if n is a perfect square, otherwise 

   282     returns False and the square root 

   283     of the next perfect square"""

   284     i = 1

   285     while i * i < n:

   286         i += 1

   287     return i * i == n, i

   288 \end{verbatim}

   289 \end{frame}

   290 \begin{frame}

   291 \frametitle{Summary}

   292 \label{sec-19}

   293 

   294 \begin{itemize}

   295 \item Functions in Python

   296 \item Passing parameters to a function

   297 \item Returning values from a function

   298 \item We also did few code reading exercises.

   299 \end{itemize}

   300 \end{frame}

   301 \begin{frame}

   302 \frametitle{Thank you!}

   303 \label{sec-20}

   304 

   305   \begin{block}{}

   306   \begin{center}

   307   This spoken tutorial has been produced by the

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

   309   \end{center}

   310   \begin{center}

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

   312       Information \& Communication Technology \\ 

   313       MHRD, Govt. of India}.

   314   \end{center}  

   315   \end{block}

   316 \end{frame}

   317 

   318 \end{document}