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-Hello friends and welcome to the tutorial on Sets
-
-{{{ Show the slide containing title }}}
-
-{{{ Show the slide containing the outline slide }}}
-
-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.
-
-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.
-
-Sets also support checking of subsets.
-::
-
- b = set([1, 2])
- b < f10
-
-gives a True since b is a proper subset of f10.
-Similarly,
-::
-
- f10 < f10
-
-gives a False since f10 is not a proper subset.
-hence the right way to do would be
-::
-
- f10 <= f10
-
-and we get a True since every set is a subset of itself.
-
-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
-::
-
- 1 in f10
- 2 in f10
-
-prints True and False respectively
-
-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.
-
-{{{ Pause here and try out the following exercises }}}
-
-%% 1 %% Given a list of marks, marks = [20, 23, 22, 23, 20, 21, 23]
- list all the duplicates
-
-{{{ continue from paused state }}}
-
-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)
-
-{{{ Show summary slide }}}
-
-This brings us to the end of the tutorial.
-we have learnt
-
- * How to make sets from lists
- * How to input sets
- * How to perform union, intersection and symmectric difference operations
- * How to check if a set is a subset of other
- * The various similarities with lists like length and containership
-
-{{{ Show the "sponsored by FOSSEE" slide }}}
-
-#[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
- Internal Reviewer 1 :
- Internal Reviewer 2 :
- External Reviewer :
-
-
-Questions
-=========
-
- 1. If ``a = [1, 1, 2, 3, 3, 5, 5, 8]``. What is set(a)
-
- a. set([1, 1, 2, 3, 3, 5, 5, 8])
- #. set([1, 2, 3, 5, 8])
- #. set([1, 2, 3, 3, 5, 5])
- #. Error
-
- Answer: set([1, 2, 3, 5, 8])
-
- 2. ``a = set([1, 3, 5])``. How do you find the length of a?
-
- Answer: len(a)
-
- 3. ``a = set([1, 3, 5])``. What does a[2] produce?
-
- a. 1
- #. 3
- #. 5
- #. Error
-
- Answer: Error
-
- 4. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
- is the value of ``odd | squares``?
-
- Answer: set([1, 3, 4, 5, 7, 9, 16])
-
- 5. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
- is the value of ``odd - squares``?
-
- Answer: set([3, 5, 7])
-
- 6. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
- is the value of ``odd ^ squares``?
-
- Answer: set([3, 4, 5, 7, 16])
-
- 7. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
- does ``odd * squares`` give?
-
- a. set([1, 12, 45, 112, 9])
- #. set([1, 3, 4, 5, 7, 9, 16])
- #. set([])
- #. Error
-
- Answer: Error
-
- 8. ``a = set([1, 2, 3, 4])`` and ``b = set([5, 6, 7, 8])``. What is ``a + b``
-
- a. set([1, 2, 3, 4, 5, 6, 7, 8])
- #. set([6, 8, 10, 12])
- #. set([5, 12, 21, 32])
- #. Error
-
- 9. ``a`` is a set. how do you check if if a varaible ``b`` exists in ``a``?
-
- Answer: b in a
-
- 10. ``a`` and ``b`` are two sets. What is ``a ^ b == (a - b) | (b - a)``?
-
- a. True
- #. False
-
- Answer: False
-
-
-Problems
-========
-
- 1. Given that mat_marks is a list of maths marks of a class. Find out the
- no.of duplicates marks in the list.
-
- Answer::
-
- unique_marks = set(mat_marks)
- no_of_duplicates = len(mat_marks) - len(unique_marks)
-
- 2. Given that mat_marks is a list of maths marks of a class. Find how many
- duplicates of each mark exist.
-
- Answer::
-
- marks_set = set(mat_marks)
- for mark in marks_set:
- occurences = mat_marks.count(mark)
- print occurences - 1, "duplicates of", mark, "exist"