IBM Data Engineer Professional Certificate - Coursera

gistfile1.txt

Sets in Python
Estimated time needed: 20 minutes

Objectives
After completing this lab you will be able to:

Work with sets in Python, including operations and logic operations.
Table of Contents
Sets
Set Content
Set Operations
Sets Logic Operations
Quiz on Sets
Sets
Set Content
A set is a unique collection of objects in Python. You can denote a set with a pair of curly brackets {}. Python will automatically remove duplicate items:

# Create a set
​
set1 = {"pop", "rock", "soul", "hard rock", "rock", "R&B", "rock", "disco"}
set1
{'R&B', 'disco', 'hard rock', 'pop', 'rock', 'soul'}
The process of mapping is illustrated in the figure:

Image
You can also create a set from a list as follows:

# Convert list to set
​
album_list = [ "Michael Jackson", "Thriller", 1982, "00:42:19", \
              "Pop, Rock, R&B", 46.0, 65, "30-Nov-82", None, 10.0]
album_set = set(album_list)             
album_set
{'00:42:19',
 10.0,
 1982,
 '30-Nov-82',
 46.0,
 65,
 'Michael Jackson',
 None,
 'Pop, Rock, R&B',
 'Thriller'}
Now let us create a set of genres:

# Convert list to set
​
music_genres = set(["pop", "pop", "rock", "folk rock", "hard rock", "soul", \
                    "progressive rock", "soft rock", "R&B", "disco"])
music_genres
{'R&B',
 'disco',
 'folk rock',
 'hard rock',
 'pop',
 'progressive rock',
 'rock',
 'soft rock',
 'soul'}
Set Operations
Let us go over set operations, as these can be used to change the set. Consider the set A:

# Sample set
​
A = set(["Thriller", "Back in Black", "AC/DC"])
A
{'AC/DC', 'Back in Black', 'Thriller'}
We can add an element to a set using the add() method:

# Add element to set
​
A.add("NSYNC")
A
{'AC/DC', 'Back in Black', 'NSYNC', 'Thriller'}
If we add the same element twice, nothing will happen as there can be no duplicates in a set:

# Try to add duplicate element to the set
​
A.add("NSYNC")
A
{'AC/DC', 'Back in Black', 'NSYNC', 'Thriller'}
We can remove an item from a set using the remove method:

# Remove the element from set
​
A.remove("NSYNC")
A
{'AC/DC', 'Back in Black', 'Thriller'}
We can verify if an element is in the set using the in command:

# Verify if the element is in the set
​
"AC/DC" in A
True
Sets Logic Operations
Remember that with sets you can check the difference between sets, as well as the symmetric difference, intersection, and union:

Consider the following two sets:

# Sample Sets
​
album_set1 = set(["Thriller", 'AC/DC', 'Back in Black'])
album_set2 = set([ "AC/DC", "Back in Black", "The Dark Side of the Moon"])
Image
# Print two sets
​
album_set1, album_set2
({'AC/DC', 'Back in Black', 'Thriller'},
 {'AC/DC', 'Back in Black', 'The Dark Side of the Moon'})
As both sets contain AC/DC and Back in Black we represent these common elements with the intersection of two circles.

Image
You can find the intersect of two sets as follow using &:

# Find the intersections
​
intersection = album_set1 & album_set2
intersection
{'AC/DC', 'Back in Black'}
You can find all the elements that are only contained in album_set1 using the difference method:

# Find the difference in set1 but not set2
​
album_set1.difference(album_set2)  
{'Thriller'}
You only need to consider elements in album_set1; all the elements in album_set2, including the intersection, are not included.

Image
The elements in album_set2 but not in album_set1 is given by:

album_set2.difference(album_set1)  
{'The Dark Side of the Moon'}
Image
You can also find the intersection of album_list1 and album_list2, using the intersection method:

# Use intersection method to find the intersection of album_list1 and album_list2
​
album_set1.intersection(album_set2)   
{'AC/DC', 'Back in Black'}
This corresponds to the intersection of the two circles:

Image
The union corresponds to all the elements in both sets, which is represented by coloring both circles:

Image
The union is given by:

# Find the union of two sets
​
album_set1.union(album_set2)
{'AC/DC', 'Back in Black', 'The Dark Side of the Moon', 'Thriller'}
And you can check if a set is a superset or subset of another set, respectively, like this:

# Check if superset
​
set(album_set1).issuperset(album_set2)   
False
# Check if subset
​
set(album_set2).issubset(album_set1)     
False
Here is an example where issubset() and issuperset() return true:

# Check if subset
​
set({"Back in Black", "AC/DC"}).issubset(album_set1) 
True
# Check if superset
​
album_set1.issuperset({"Back in Black", "AC/DC"})   
True
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Quiz on Sets
Convert the list ['rap','house','electronic music', 'rap'] to a set:

set(rap_list)
# Write your code below and press Shift+Enter to execute
set(['rap','house','electronic music', 'rap'])
{'electronic music', 'house', 'rap'}
Click here for the solution
Consider the list A = [1, 2, 2, 1] and set B = set([1, 2, 2, 1]), does sum(A) == sum(B)?

# Write your code below and press Shift+Enter to execute
A = [1, 2, 2, 1]
print(A)
print(sum(A))
B = set([1, 2, 2, 1])
print(B)
print(sum(B))
A == B
[1, 2, 2, 1]
6
{1, 2}
3
False
Click here for the solution
A = [1, 2, 2, 1]  
B = set([1, 2, 2, 1])
print("the sum of A is:", sum(A))
print("the sum of B is:", sum(B))
Create a new set album_set3 that is the union of album_set1 and album_set2:

lbum_set3
# Write your code below and press Shift+Enter to execute
​
album_set1 = set(["Thriller", 'AC/DC', 'Back in Black'])
album_set2 = set([ "AC/DC", "Back in Black", "The Dark Side of the Moon"])
​
album_set3 = album_set1.union(album_set2)
print(album_set3)
{'Back in Black', 'Thriller', 'The Dark Side of the Moon', 'AC/DC'}
Click here for the solution
Find out if album_set1 is a subset of album_set3:

# Write your code below and press Shift+Enter to execute
album_set1.issubset(album_set3)
True
Click here for the solution