Python-3.4.3/C3/Sets-in-Python/English-timed

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Time
Narration
00:01 Welcome to the spoken tutorial on Sets in Python.
00:06 In this tutorial, you will learn to, Create sets from lists
00:12 Perform union, intersection and symmetric difference operations
00:18 Check if a set is a subset of other and

Understand various similarities with lists

00:27 To record this tutorial, I am using

Ubuntu Linux 16.04 operating system

00:35 Python 3.4.3 and IPython 5.1.0
00:42 To practise this tutorial, you should know how to run basic Python commands on the ipython console and use lists
00:53 If not, see the relevant Python tutorials on this website.
00:58 First let us see the overview of sets.
01:02 Sets are unordered collections of unique elements.
01:07 The set itself is mutable.

We can add or remove items from it.

01:14 Let us start ipython.

Open the terminal.

01:19 Type ipython3 and press Enter.
01:24 From here onwards, remember to press the Enter key after typing every command on the terminal.
01:31 Let us look at how to input sets.
01:35 Type,

a underscore list is equal to inside square brackets 1 comma 2 comma 1 comma 4 comma 5 comma 6 comma 2

01:47 Type, a is equal to set inside brackets a underscore list
01:54 Then type, a
01:57 We can see that duplicates are removed and the set contains only unique elements.
02:03 Sets can also be created directly as follows
02:08 Type, b is equal to inside curly braces 1 comma 2 comma 1 comma 4 comma 5 comma 6 comma 2
02:19 Type, b. As before, we see that the set contains only unique elements.
02:27 To create an empty set, type, c is equal to set open and close brackets
02:36 Note that d is equal to open and close curly braces creates an empty dictionary, not an empty set.
02:45 Sets can contain numbers, strings and tuples.

But cannot contain mutable elements such as lists or dictionaries.

02:56 Type, b underscore list is equal to inside square brackets again inside square brackets 1 comma 2 comma 1 comma 6 comma 2
03:09 Now type, b is equal to set inside brackets b underscore list
03:17 As you can see, it gives a TypeError.
03:21 Now let us perform some operations on sets.

For this, we will first create a pair of sets.

03:29 Type the sets as shown.
03:33 Here, f is the set of fibonacci numbers from 1 to 10.
03:39 And p is the set of prime numbers from 1 to 15.
03:44 Various operations can be performed on sets.
03:47 First we will add an element to a set by using add method.
03:53 Type, f dot add inside brackets 13
03:58 Now type, f

As you can see, 13 is added to the set f.

04:06 add method has no effect if the element is already present.
04:11 Type, f dot add inside brackets 13
04:16 Type, f

As you can see, 13 is not added this time.

04:23 Next we will learn to remove an element using remove method.
04:28 Type, p dot remove inside brackets 13
04:34 Now type, p. As you can see, 13 is removed from the set p.
04:41 If the element is not a member, it raises a KeyError.
04:46 Type, p dot remove inside brackets 18
04:52 KeyError is raised since element 18 is not present in p.
04:57 The pipe character stands for union.
05:01 Type, f pipe p
05:06 Or type, f dot union inside brackets p

It gave the union of f and p

05:16 The ampersand character stands for intersection.
05:20 Type, f ampersand p

Or type, f dot intersection inside brackets p

05:30 It gave the intersection of f and p.
05:34 Type, f minus p

Or type, f dot difference inside brackets p

05:44 It gave all the elements that are in f but not in p.
05:50 Type, f caret p
05:54 Or type, f dot symmetric underscore difference inside brackets p
06:01 It gives all the elements in f union p but not in f intersection p.
06:08 In mathematical terms, it gives the symmetric difference.
06:13 Sets also support checking of subsets.
06:17 Type, a is equal to set inside brackets inside square brackets 1 comma 2 comma 3 comma 4
06:27 Type, b is equal to set inside brackets inside square brackets 1 comma 2
06:35 Now type, b less than or equal to a

Or type, b dot issubset inside brackets a

06:47 It gives True since b is a subset of a.
06:52 Sets also support checking of supersets.

Type, b greater than or equal to a

07:01 Or type, b dot issuperset inside brackets a
07:08 We get False since b is not a superset of a.
07:14 Every set is a subset as well as a superset of itself.
07:20 Type, a less than or equal to a

a greater than or equal to a

07:28 It gives True in both cases since a is a superset and subset of itself.
07:35 Elements of a set can be accessed using for loop.
07:39 Type, for x in a colon print inside brackets x
07:47 The items from the set will not appear in any specific order.
07:52 The length and containership check on sets are similar as in lists and tuples.
07:59 Type, len inside brackets a

It shows 4.

08:07 Type,

1 in a

7 in a

08:13 It prints True and False respectively
08:18 Sets do not support indexing.

Hence, slicing and striding are not valid on sets.

08:25 Pause the video.

Try this exercise and then resume the video.

08:31 Given a list of marks, as shown, list all the duplicate marks.
08:37 Switch to the terminal for the solution.
08:41 Type, marks is equal to inside square brackets 20 comma 23 comma 22 comma 23 comma 20 comma 21 comma 23
08:53 marks underscore set is equal to set inside brackets marks
09:00 for num in marks underscore set colon

marks dot remove inside brackets num

09:10 remove method only removes the first occurrence of an element from the list.
09:17 Type, duplicates is equal to set inside bracket marks
09:24 Now type, duplicates
09:28 We now have duplicate marks in the set duplicates.

Hence, we have obtained our required solution.

09:37 This brings us to the end of this tutorial. Let us summarize.
09:43 In this tutorial, we have learnt to, Make sets from lists or by using curly braces
09:50 Perform union, intersection and symmetric difference operations
09:55 Check if a set is a subset of other using the less than or equal to operator
10:02 Understand the various similarities with lists like length and containership
10:08 Here are some self assessment questions for you to solve.
10:12 First. If a is assigned as follows, what is set of a
10:18 Second. Given odd and squares as shown. How do you find the symmetric difference of these two sets?
10:27 Third. If a is a set, how do you check if a variable b exists in a?
10:34 And the answers,

First. set of a will have all the common elements in the list a, that is 1 comma 2 comma 3 comma 5 comma 8.

10:46 Second. To find the symmetric difference between two sets, we use the operator caret. So we can type odd caret squares
10:56 Third. To check the containership, we type, b in a
11:01 Please post your timed queries in this forum.
11:05 Please post your general queries on Python in this forum.
11:10 FOSSEE team coordinates the TBC project.
11:15 Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

11:25 This is Priya from IIT Bombay signing off.

Thanks for watching.

Contributors and Content Editors

PoojaMoolya