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+#+LaTeX_CLASS_OPTIONS: [presentation]
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+#+LaTeX_HEADER:\lstset{language=Python, basicstyle=\ttfamily\bfseries,
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+
+#+TITLE:  Getting started with functions
+#+AUTHOR:  FOSSEE
+#+EMAIL:   info@fossee.in
+#+DATE:    
+
+#+DESCRIPTION: 
+#+KEYWORDS: 
+#+LANGUAGE:  en
+#+OPTIONS:   H:3 num:nil toc:nil \n:nil @:t ::t |:t ^:t -:t f:t *:t <:t
+#+OPTIONS:   TeX:t LaTeX:nil skip:nil d:nil todo:nil pri:nil tags:not-in-toc
+
+* Outline
+  - Define functions
+  - Pass arguments to functions
+  - Learn about docstrings
+  - Return values from functions
+
+* Function
+  - Eliminate code redundancy
+  - Help in code reuse
+  - Subroutine
+    - relatively independent of remaining code
+
+* ~f(x)~ a mathematical function
+
+  $f(x) = x^{2}$
+
+  : f(1) -> 1
+  : f(2) -> 4
+
+* Define ~f(x)~ in Python
+  #+begin_src python
+    def f(x):
+        return x*x
+  #+end_src
+
+  - ~def~ - keyword
+  - ~f~ - function name
+  - ~x~ - parameter / argument to function ~f~
+
+* Exercise 1
+
+  Write a python function named ~cube~ which computes the cube of a given
+  number ~n~.
+  
+  - Pause here and try to solve the problem yourself.
+
+* Solution
+  #+begin_src python
+    def cube(n):
+    	return n**3
+  #+end_src
+
+* ~greet~ function
+
+ Function ~greet~ which will print ~Hello World!~.
+ #+begin_src python
+    def greet():
+    	print "Hello World!"
+ #+end_src
+  - Call the function ~greet~
+    : In []: greet()
+    : Hello World!
+
+* Exercise 2
+
+  Write a python function named ~avg~ which computes the average of
+  ~a~ and ~b~.
+
+  - Pause here and try to solve the problem yourself.
+
+* Solution 2
+ #+begin_src python
+    def avg(a,b):
+    	return (a + b)/2
+ #+end_src
+
+ - ~a~ and ~b~ are parameters
+ - ~def f(p1, p2, p3, ... , pn)~
+
+* Docstring
+
+  - Documenting/commenting code is a good practice
+   #+begin_src python
+     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_src
+  - Docstring
+    - written in the line after the ~def~ line.
+    - Inside triple quote.
+  - Documentation
+    : avg?
+* Exercise 3
+  Add docstring to the function f.
+
+* Solution 3
+
+#+begin_src python
+  def f(x):
+      """Accepts a number x as argument and,
+      returns the square of the number x."""
+      return x*x
+#+end_src
+
+* Exercise 4
+  Write a python function named ~circle~ which returns the area and
+  perimeter of a circle given radius ~r~.
+
+* Solution 4
+#+begin_src python
+  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_src
+
+* ~what~
+#+begin_src python
+
+ def what( n ):
+     if n < 0: n = -n
+     while n > 0:
+         if n % 2 == 1:
+             return False
+         n /= 10
+     return True
+#+end_src
+
+* ~even_digits~
+#+begin_src python
+ 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_src
+
+* ~what~
+#+begin_src python
+ def what( n ):
+     i = 1
+     while i * i < n:
+         i += 1
+     return i * i == n, i
+#+end_src
+
+* ~is_perfect_square~
+#+begin_src python
+ 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_src
+
+* Summary
+ - Functions in Python
+ - Passing parameters to a function
+ - Returning values from a function
+
+ - We also did few code reading exercises.
+
+* Thank you!
+#+begin_latex
+  \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_latex