Defining Funtions And The range() Function

Defining Functions

     We can define function by using def keyword, the function definition written by using def keyword with function name followed by parameters enclosed by simple parenthesis or can be blank. The next statement is at next line with indent. It can have docstring.
Example:
     Lets write function for checking number is prime or not. 
>>> def check_prime(num):
...     is_prime = True
...     for index in range(2, num):
...         if num % index == 0:
...             is_prime = False
...                 break
...         index += 1
...     if is_prime:
...         print "Given Number is Prime"
...     else:
...         print "Given Number is Not Prime"
...
>>> check_prime(9)
Given Number is Prime
>>> check_prime(8)
Given Number is Not Prime
     Function parameters can have Default Argument, Variable Number of Arguments, Keyword Arguments.

Default Arguments

     A function can have default arguments as shown below:- 
>>> def modify_me(limit, text = "Their"):
...     for i in range(limit):
...         print "Hello " + text
...
     This function can be called with mandatory argument as:- 
>>> modify_me(3):
Hello Their
Hello Their
Hello Their
     Or with optional arguments as:- 
>>> modify_me(3, 'World')
Hello World
Hello World
Hello World

Keyword Arguments

     A function can be called with keyword arguments, i.e. keyword=value, as shown below:- 
>>> def greet(limit, greetings = "Hello", whom = "Their"):
...     for i in range(limit):
...         print greetings + ' ' + whom
...
     This function can be called with mandatory argument as:- 
>>> greet(1):
Hello Their
     Or with optional keyword arguments as:- 
>>> greet(3, 'World')
Hello World
Hello World
Hello World
     Or giving keyword arguments as:- 
>>> greet(3, greetings='Good Morning', whom='Dear')
Good Morning Dear
Good Morning Dear
Good Morning Dear

Variable Or Arbitrary Arguments

     It can be used when you don't know
  1. How many arguments are there?
  2. How many of them keywords?

>>> def greet(limit, greetings = "Hello", whom = "Their"):
...     for i in range(limit):
...         print greetings + ' ' + whom
...
     This function can be called with mandatory argument as:- 
>>> greet(1):
Hello Their
     Or with optional keyword arguments as:- 
>>> greet(3, 'World')
Hello World
Hello World
Hello World
     Or giving keyword arguments as:- 
>>> greet(3, greetings='Good Morning', whom='Dear')
Good Morning Dear
Good Morning Dear
Good Morning Dear

range Function

     If you do need to iterate over a sequence of numbers, the built-in function range() comes in handy. It generates arithmetic progressions: 
>>> for i in range(10):
...     print i,
...
0 1 2 3 4 5 6 7 8 9
This will print nothing.
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