.. Objectives

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

.. Prerequisites

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

..   1. Getting started with lists

.. Author              : Nishanth Amuluru

   Internal Reviewer   : 

   External Reviewer   :

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

Script

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In this tutorial, we shall learn

 * what are tuples

 * their similarities and dissimilarities with lists

 * why are they needed

::

    t = (1, 2.5, "hello", -4, "world", 1.24, 5)

    t

defines a tuple. The items in the tuple are indexed using numbers and can be 

accessed by using their position.

::

    t[3]

prints -4 which is the fourth item of the tuple.

::

    t[1:5:2]

prints the corresponding slice

This is the behaviour similar as to lists. But the difference can be seen when

we try to change an element in the tuple.

::

    t[2] = "Hello"

We can see that, it raises an error saying tuple does not support item

We shall understand that soon. But let us look at a simple problem of swapping

values.

{{{ Pause here and try out the following exercises }}}

%% 1 %% a = 5 and b = 7. swap the values of a and b

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::

    a = 5

    b = 7

    a

    b

We define the two values

::

    temp = a

    a = b

    b = temp

    a

    b

This is the traditional approach

Now let us do it the python way

::

    a

    b

    a, b = b, a

    a

    b

::

    a = 2.5

    b = "hello"

    a

    b

This is possible because of the immutability of tuples. This process is called

tuple packing and unpacking.

Let us first see what is tuple packing. Type

::

    5,

What we see is a tuple with one element.

::

    5, "hello", 2.5

So when we are actually typing two or more elements seperated by commas, those

When you type

::

    a, b = b, a

First the values of b and a are packed into a tuple on the right side and then

unpacked into the variables a and b.

Immutability of tuples ensures that the values are not changed during the

packing and unpacking.

{{{ Show summary slide }}}

This brings us to the end of the tutorial.

we have learnt

 * How to define tuples

 * The similarities of tuples with lists, like indexing and iterability

 * The immutability of tuples

 * The value swapping idiom in Python

 * packing and unpacking of tuples

{{{ Show the "sponsored by FOSSEE" slide }}}

This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India

Hope you have enjoyed and found it useful.