Hello friends and welcome to the tutorial on Sets

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In this tutorial, we shall learn

 * sets

 * operations on sets

Sets are data structures which contain unique elements. In other words,

duplicates are not allowed in sets.

Lets look at how to input sets.

type

::

    a_list = [1, 2, 1, 4, 5, 6, 7]

    a = set(a_list)

    a

We can see that duplicates are removed and the set contains only unique

elements. 

::

    f10 = set([1, 2, 3, 5, 8])

    p10 = set([2, 3, 5, 7])

f10 is the set of fibonacci numbers from 1 to 10.

p10 is the set of prime numbers from 1 to 10.

Sets can be iterated upon just like lists and tuples. 

::

    for i in f10:

        print i,

prints the elements of f10.

The length and containership check on sets is similar as in lists and tuples.

::

    len(f10)

shows 5. And

::

    2 in f10

prints False

The order in which elements are organised in a set is not to be relied upon 

since sets do not support indexing. Hence, slicing and striding are not valid

on sets.

Various operations that we do on sets are possible here also.

The | character stands for union

::

    f10 | p10

gives us the union of f10 and p10

The & character stands for intersection.

::

    f10 & p10

gives the intersection

similarly,

::

    f10 - p10

gives all the elements that are in f10 but not in p10

::

    f10 ^ p10

is all the elements in f10 union p10 but not in f10 intersection p10. In

mathematical terms, it gives the symmectric difference.

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%% 1 %% Given a list of marks, marks = [20, 23, 22, 23, 20, 21, 23] 

        list all the duplicates

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Duplicates marks are the marks left out when we remove each element of the 

list exactly one time.

::

    marks = [20, 23, 22, 23, 20, 21, 23] 

    marks_set = set(marks)

    for mark in marks_set:

        marks.remove(mark)

    # we are now left with only duplicates in the list marks

    duplicates = set(marks)

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This brings us to the end of the tutorial.

we have learnt

 * How to make sets from lists

 * How to input sets

 * The various similarities with lists like length and containership

 * How to perform union, intersection and symmectric difference operations

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#[Nishanth]: Will add this line after all of us fix on one.

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

Hope you have enjoyed and found it useful.

Thankyou

.. Author              : Nishanth

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