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+.. Objectives
+.. ----------
+
+.. Clearly state the objectives of the LO (along with RBT level)
+
+.. Prerequisites
+.. -------------
+
+.. 1. getting started with lists
+.. 2.
+.. 3.
+
+.. Author : Madhu
+ Internal Reviewer : Punch
+ External Reviewer :
+ Language Reviewer : Bhanukiran
+ Checklist OK? : <16-11-2010, Anand, OK> [2010-10-05]
+
+Script
+------
+
+{{{ Show the slide containing the title }}}
+
+Hello friends. Welcome to this spoken tutorial on Manipulating Lists.
+
+{{{ Show the slide containing the outline }}}
+
+We have already learnt about Lists in Python. In this tutorial,
+we will learn about more advanced features of Lists in Python like how
+to concatenate two lists, details of slicing and striding of lists,
+methods to sort and reverse lists.
+
+{{{ Shift to terminal and start ipython }}}
+
+To begin with let us start ipython, by typing::
+
+ ipython
+
+on the terminal
+
+We already know what Lists are in Python, how to access individual
+elements in the list and some of the functions that can be run on the
+lists like ``max, min, sum, len`` and so on. Now let us learn some of
+the basic operations that can be performed on Lists.
+
+We already know how to access individual elements in a List. But what
+if we have a scenario where we need to get a part of the entire list
+or what we call as a slice of the list? Python supports slicing on
+lists. Let us say I have the list::
+
+ primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
+
+To obtain all the primes between 10 and 20 from the above list of
+primes we say::
+
+ primes[4:8]
+
+This gives us all the elements in the list starting from the element
+with the index 4, which is 11 in our list, upto the element with index 8
+in the list but not including the eigth element. So we obtain a slice
+starting from 11 upto 19th. It is a very important to remember that
+whenever we specify a range of elements in Python the start index is
+included and end index is not included. So in the above case, 11 which
+was the element with the index 4 was included but 23 which was the
+element with index 8 was excluded.
+
+Following is an exercise you must do.
+
+%% %% Obtain the primes less than 10, from the list ``primes``.
+
+Please, pause the video here, do the exercise and then resume.
+
+::
+
+ primes[0:4]
+
+will give us the primes below 10.
+
+Generalizing, we can obtain a slice of the list "p" from the index
+"start" upto the index "end" but excluding "end" with the following
+syntax
+
+{{{ Show the slide containing p[start:stop] }}}
+
+By default the slice fetches all the elements between start and stop
+including start but not stop. So as to say we obtain all the elements
+between start and stop in steps of one. Python also provides us the
+functionality to specify the steps in which the slice must be
+obtained. Say we have::
+
+ num = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
+
+If we want to obtain all the odd numbers less than 10 from the list
+``num`` we have to start from element with index 1 upto the index 10 in
+steps of 2::
+
+ num[1:10:2]
+
+When no step is specified, it is assumed to be 1. Similarly, there are
+default values for start and stop indices as well. If we don't specify
+the start index it is implicitly taken as the first element of the
+list::
+
+ num[:10]
+
+This gives us all the elements from the beginning upto the 10th
+element but not including the 10th element in the list "num". Similary
+if the stop index is not specified it is implicitly assumed to be the
+end of the list, including the last element of the list::
+
+ num[10:]
+
+gives all the elements starting from the 10th element in the list
+"num" upto the final element including that last element. Now::
+
+ num[::2]
+
+gives us all the even numbers in the list "num".
+
+Following is an exercise that you must do.
+
+%% %% Obtain all the multiples of three from the list ``num``.
+
+Please, pause the video here. Do the exercise and then continue.
+
+::
+
+ num[::3]
+
+gives us all the multiples of 3 from the list, since every third
+element in it, starting from 0, is divisible by 3.
+
+The other basic operation that we can perform on lists is concatenation
+of two or more lists. We can combine two lists by using the "plus"
+operator. Say we have
+
+{{{ Read as you type }}}::
+
+ a = [1, 2, 3, 4]
+ b = [4, 5, 6, 7]
+ a + b
+
+When we concatenate lists using the "plus" operator we get a new
+list. We can store this list in a new variable::
+
+ c = a + b
+ c
+
+It is important to observe that the "plus" operator always returns a
+new list without altering the lists being concatenated in any way.
+
+We know that a list is a collection of data. Whenever we have a
+collection we run into situations where we want to sort the
+collection. Lists support sort method which sorts the list inplace::
+
+ a = [5, 1, 6, 7, 7, 10]
+ a.sort()
+
+Now the contents of the list ``a`` will be::
+
+ a
+ [1, 5, 6, 7, 7, 10]
+
+As the sort method sorts the elements of a list, the original list we had
+is overwritten or replaced. We have no way to obtain the original list
+back. One way to avoid this is to keep a copy of the original list in
+another variable and run the sort method on the list. However Python
+also provides a built-in function called sorted which sorts the list
+which is passed as an argument to it and returns a new sorted list::
+
+ a = [5, 1, 6, 7, 7, 10]
+ sorted(a)
+
+We can store this sorted list another list variable::
+
+ sa = sorted(a)
+
+Python also provides the reverse method which reverses
+the list inplace::
+
+ a = [1, 2, 3, 4, 5]
+ a.reverse()
+
+reverses the list "a" and stores the reversed list inplace i.e. in "a"
+itself. Lets see the list "a"::
+
+ a
+ [5, 4, 3, 2, 1]
+
+But again the original list is lost.
+.. #[punch: removed reversed, since it returns an iterator]
+
+To reverse a list, we could use striding with negative indexing.::
+
+ a[::-1]
+
+We can also store this new reversed list in another list variable.
+
+Following is an (are) exercise(s) that you must do.
+
+%% %% Given a list of marks of students in an examination, obtain a
+ list with marks in descending order.
+ ::
+
+ marks = [99, 67, 47, 100, 50, 75, 62]
+
+Please, pause the video here. Do the exercise(s) and then continue.
+
+::
+
+ sorted(marks)[::-1]
+
+OR
+
+::
+
+ sorted(marks, reverse = True)
+
+
+
+{{{ Show summary slide }}}
+
+This brings us to the end of another session. In this tutorial session
+we learnt
+
+ * Obtaining parts of lists using slicing and striding
+ * List concatenation
+ * Sorting lists
+ * Reversing lists
+
+{{{ 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.
+Thank you!
+
+