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#+TITLE:    
#+AUTHOR:    FOSSEE
#+EMAIL:     
#+DATE:    

#+DESCRIPTION: 
#+KEYWORDS: 
#+LANGUAGE:  en
#+OPTIONS:   H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
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* 
#+begin_latex
\begin{center}
\vspace{12pt}
\textcolor{blue}{\huge Advanced features of Functions}
\end{center}
\vspace{18pt}
\begin{center}
\vspace{10pt}
\includegraphics[scale=0.95]{../images/fossee-logo.png}\\
\vspace{5pt}
\scriptsize Developed by FOSSEE Team, IIT-Bombay. \\ 
\scriptsize Funded by National Mission on Education through ICT\\
\scriptsize  MHRD,Govt. of India\\
\includegraphics[scale=0.30]{../images/iitb-logo.png}\\
\end{center}
#+end_latex
* Objectives
 At the end of this tutorial, you will be able to, 

 - Assign default values to arguments, when defining functions.
 - Define and call functions with keyword arguments. 
 - Learn some of the built-in functions available in Python standard 
    library and the scientific computing libraries.
* Pre-requisite
Spoken tutorial on -
- Getting started with functions
* Functions
#+begin_src Python
s.strip() # strips on spaces. 
s.strip('@') # strips the string of '@' symbols.

plot(x, y) # plots with x vs. y using default line style. 
plot(x, y, 'o') # plots x vs. y with circle markers. 

linspace(0, 2*pi, 100) # returns 100 points between 0 and 2pi
linspace(0, 2*pi) # returns 50 points between 0 and 2pi
#+end_src
* Exercise 1
 - Redefine the function ~welcome~, by interchanging it's
  arguments.
  Place the ~name~ argument with it's default value of
  "World" before the ~greet~ argument.
* Solution 1
  #+begin_src python
    def welcome(name="World", greet):
        print greet, name
  #+end_src
  We get an error that reads ~SyntaxError: non-default argument follows 
  default argument~. When defining a function all the
  argument with default values should come at the end.

* Exercise 2
 - See the definition of linspace using ~?~ and make a note of all the
  arguments with default values are towards the end.
* Exercise 3
 - Redefine the function ~welcome~ with a default value of
  "Hello" to the ~greet~ argument. 
  Then, call the function without any arguments. 
* Keyword arguments examples
#+begin_src Python
legend(['sin(2y)'], loc = 'center')

plot(y, sin(y), 'g', linewidth = 2)

annotate('local max', xy = (1.5, 1))

pie(science.values(), labels = science.keys())
#+end_src
* Built-in functions
#+begin_src Python
  Math functions - abs, sin, ....
 
  Plot functions - plot, bar, pie ...
 
  Boolean functions - and, or, not ...
#+end_src
* Classes of functions
#+begin_src Python
- pylab
  - plot, bar, contour, boxplot, errorbar, log, polar, quiver, semilog

- scipy (modules)
  - fftpack, stats, linalg, ndimage, signal, optimize, integrate
#+end_src
* Summary
 In this tutorial, we have learnt to, 

 - Define functions with default arguments.
 - Call functions using keyword arguments.
 - Use the range of functions available in the Python standard library 
   and the Scientific Computing related packages. 

* Evaluation
1. All arguments of a function cannot have default values. 
   - True or False? 

2. The following is a valid function definition. True or False? 
#+begin_src Python
def seperator(count=40, char, show=False):
     if show:
          print char * count
     return char * count
#+end_src
3. When calling a function, 

   - the arguments should always be in the order in which they are defined.
   - only keyword arguments can be in any order, but should be called
     at the beginning.
   - only keyword arguments can be in any order, but should be called
     at the end.
* Solutions
1. False

2. False

3. only keyword arguments can be in any order, 
   but should be called at the end
* 
#+begin_latex
  \begin{block}{}
  \begin{center}
  \textcolor{blue}{\Large THANK YOU!} 
  \end{center}
  \end{block}
\begin{block}{}
  \begin{center}
    For more Information, visit our website\\
    \url{http://fossee.in/}
  \end{center}  
  \end{block}
#+end_latex