1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
|
.. Objectives
.. ----------
.. A - Students and teachers from Science and engineering backgrounds
B - Will learn what are tuples and why they are needed
Will learn the various methods of accessing elements in tuples
C -
D -
.. 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
------
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
|
