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\usepackage{listings}

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

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\title{Getting started with functions}

\author{FOSSEE}

\date{}

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

\begin{document}

\maketitle

\begin{frame}

\frametitle{Outline}

\label{sec-1}

\begin{itemize}

\item Define functions

\item Pass arguments to functions

\item Learn about docstrings

\item Return values from functions

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Function}

\label{sec-2}

\begin{itemize}

\item Eliminate code redundancy

\item Help in code reuse

\item Subroutine

\begin{itemize}

\item relatively independent of remaining code

\end{itemize}

\end{itemize}

\end{frame}

\begin{frame}[fragile]

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

\label{sec-3}

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

\begin{verbatim}

   f(1) -> 1

   f(2) -> 4

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

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

\label{sec-4}

\begin{verbatim}

def f(x):

    return x*x

\end{verbatim}

\begin{itemize}

\item \texttt{def} - keyword

\item \texttt{f} - function name

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

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Exercise 1}

\label{sec-5}

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

  number \texttt{n}.

\begin{itemize}

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

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Solution}

\label{sec-6}

\begin{verbatim}

def cube(n):

    return n**3

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

\frametitle{\texttt{greet} function}

\label{sec-7}

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

\begin{verbatim}

def greet():

    print "Hello World!"

\end{verbatim}

\begin{itemize}

\item Call the function \texttt{greet}

\begin{verbatim}

     In []: greet()

     Hello World!

\end{verbatim}

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Exercise 2}

\label{sec-8}

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

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

\begin{itemize}

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

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Solution 2}

\label{sec-9}

\begin{verbatim}

def avg(a,b):

    return (a + b)/2

\end{verbatim}

\begin{itemize}

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

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

\end{itemize}

\end{frame}

\begin{frame}[fragile]

\frametitle{Docstring}

\label{sec-10}

\begin{itemize}

\item Documenting/commenting code is a good practice

\begin{verbatim}

def avg(a,b):

    """ avg takes two numbers as input 

    (a & b), and returns the average 

    of a and b"""

    return (a+b)/2

\end{verbatim}

\item Docstring

\begin{itemize}

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

\item Inside triple quote.

\end{itemize}

\item Documentation

\begin{verbatim}

     avg?

\end{verbatim}

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Exercise 3}

\label{sec-11}

  Add docstring to the function f.

\end{frame}

\begin{frame}[fragile]

\frametitle{Solution 3}

\label{sec-12}

\begin{verbatim}

def f(x):

    """Accepts a number x as argument and,

    returns the square of the number x."""

    return x*x

\end{verbatim}

\end{frame}

\begin{frame}

\frametitle{Exercise 4}

\label{sec-13}

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

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

\end{frame}

\begin{frame}[fragile]

\frametitle{Solution 4}

\label{sec-14}

\begin{verbatim}

def circle(r):

    """returns area and perimeter of a circle given 

    radius r"""

    pi = 3.14

    area = pi * r * r

    perimeter = 2 * pi * r

    return area, perimeter

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

\frametitle{\texttt{what}}

\label{sec-15}

\begin{verbatim}

def what( n ):

    if n < 0: n = -n

    while n > 0:

        if n % 2 == 1:

            return False

        n /= 10

    return True

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

\frametitle{\texttt{even\_digits}}

\label{sec-16}

\begin{verbatim}

def even_digits( n ):

   """returns True if all the digits of number 

   n is even returns False if all the digits 

   of number n is not even"""

    if n < 0: n = -n

    while n > 0:

        if n % 2 == 1:

            return False

        n /= 10

    return True

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

\frametitle{\texttt{what}}

\label{sec-17}

\begin{verbatim}

def what( n ):

    i = 1

    while i * i < n:

        i += 1

    return i * i == n, i

\end{verbatim}

\end{frame}

\begin{frame}[fragile]

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

\label{sec-18}

\begin{verbatim}

def is_perfect_square( n ):

    """returns True and square root of n, 

    if n is a perfect square, otherwise 

    returns False and the square root 

    of the next perfect square"""

    i = 1

    while i * i < n:

        i += 1

    return i * i == n, i

\end{verbatim}

\end{frame}

\begin{frame}

\frametitle{Summary}

\label{sec-19}

\begin{itemize}

\item Functions in Python

\item Passing parameters to a function

\item Returning values from a function

\item We also did few code reading exercises.

\end{itemize}

\end{frame}

\begin{frame}

\frametitle{Thank you!}

\label{sec-20}

  \begin{block}{}

  \begin{center}

  This spoken tutorial has been produced by the

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

  \end{center}

  \begin{center}

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

      Information \& Communication Technology \\ 

      MHRD, Govt. of India}.

  \end{center}  

  \end{block}

\end{frame}

\end{document}