.. Objectives

.. ----------

.. By the end of this tutorial, you will be able to

.. Create Lists.

.. Access List elements.

.. Append elemets to list

.. Delete list elemets

.. 1. getting started with ipython 

.. Prerequisites

.. -------------

..   1. getting started with strings

..   #. getting started with lists

..   #. basic datatypes

.. Author              : Puneeth 

   Internal Reviewer   : Amit 

   External Reviewer   :

   Checklist OK?       : <put date stamp here, if OK> [2010-10-05]

Script

------

Hello friends and welcome to the tutorial on getting started with

lists.

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In this tutorial we will be getting acquainted with a python data

structure called lists.  We will learn ::

 * How to create lists

 * Structure of lists

 * Access list elements

 * Append elements to lists

 * Deleting elements from lists

List is a compound data type, it can contain data of other data

types. List is also a sequence data type, all the elements are in

order and there order has a meaning.

We will first create an empty list with no elements. On your IPython

shell type ::

   empty = [] 

   type(empty)

This is an empty list without any elements.

* Filled lists

Lets now define a list, nonempty and fill it with some random elements.

nonempty = ['spam', 'eggs', 100, 1.234]

Thus the simplest way of creating a list is typing out a sequence 

of comma-separated values (items) between square brackets. 

All the list items need not have the same data type.

As we can see lists can contain different kinds of data. In the

previous example 'spam' and 'eggs' are strings and 100 and 1.234

integer and float. Thus we can put elements of heterogenous types in

lists. Thus list themselves can be one of the element types possible

in lists. Thus lists can also contain other lists.  Example ::

      list_in_list=[[4,2,3,4],'and', 1, 2, 3, 4]

We access list elements using the number of index. The

index begins from 0. So for list nonempty, nonempty[0] gives the

first element, nonempty[1] the second element and so on and

nonempty[3] the last element. ::

	    nonempty[0] 

	    nonempty[1] 

	    nonempty[3]

We can also access the elememts from the end using negative indices ::

   nonempty[-1] 

   nonempty[-2] 

   nonempty[-4]

-1 gives the last element which is the 4th element , -2 second to last and -4 gives the fourth

from last element which is first element.

We can append elements to the end of a list using append command. ::

   nonempty.append('onemore') 

   nonempty

   nonempty.append(6) 

   nonempty

As we can see non empty appends 'onemore' and 6 at the end.

Using len function we can check the number of elements in the list

nonempty. In this case it being 6 ::

	 len(nonempty)

Just like we can append elements to a list we can also remove them.

There are two ways of doing it. One is by using index. ::

      del(nonempty[1])

deletes the element at index 1, i.e the second element of the

list, 'eggs'. The other way is removing element by content. Lets say

one wishes to delete 100 from nonempty list the syntax of the command

should be :: 

      nonempty.remove(100)

but what if their were two 100's. To check that lets do a small

experiment. ::

	   nonempty.append('python') 

	   nonempty

	   nonempty.remove('python') 

	   nonempty

If we check a now we will see that the first occurence 'spam' is removed

thus remove removes the first occurence of the element in the sequence

and leaves others untouched.

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In this tutorial we came across a sequence data type called lists. ::

 * We learned how to create lists.  

 * How to access lists.

 * Append elements to list.

 * Delete Element from list.  

 * And Checking list length.

{{{ Sponsored by Fossee Slide }}}

This tutorial was created as a part of FOSSEE project.

I hope you found this tutorial useful.

Thank You

 * Author : Amit Sethi 

 * First Reviewer : 

 * Second Reviewer : Nishanth