Creating a Set

• Sets are created by using a set of curly braces ({})
• Other data types can be type-casted as a set by using its constructor

setExample1 = {"4061CEM", "Programming", "Algorithms"}
setExample2 = set(["4061CEM", "Programming", "Algorithms"])

Items of a Set

• The items of a set can be any data type
  • i.e. it can be a mixture of data types such as booleans, strings or integers
• However, the list, tuple and set data types cannot be hashed or used inside of a set

setExample1 = {"4061CEM", "Programming", "Algorithms"}
setExample2 = {4061, "Programming and Algorithms", True}

Accessing Set Items

• Items cannot be accessed in a set by referring to it via an index
• Instead, items can be accessed using a for loop

Modifying a Set (1)

• Sets are considered to be mutable, and as such we are able to add and remove items to them

Adding an Item

• Items can be added into the set using the add() function

setExample1 = {"4061CEM", "Programming", "Algorithms"}

setExample1 = {"4061CEM", "Programming", "Algorithms"}

Modifying a Set (2)

Removing Items from a Set i

• Items can be removed from a set using the remove() function
  • this will search the set for a specific value and then remove it
• If the item does not exist, an error will be thrown

setExample1 = {"4061CEM", "Programming", "Algorithms"}

setExample1.remove("Programming")

Modifying a Set (3)

Removing Items from a Set ii

• Items can also be removed from a set using the pop() function
• This will only remove the last item from the set
  • but you will not know which item will be removed, as the items in a set can constantly change index

setExample1 = {"4061CEM", "Programming", "Algorithms"}

setExample1.pop()

Modifying a Set (4)

Removing Items from a Set iii

• Items can also be removed from a set using the discard() function
  • this will search the set for a specific value and then remove it
• If the item does not exist an error *will not** be thrown

setExample1 = {"4061CEM", "Programming", "Algorithms"}

setExample1.discard("Programming")

Modifying a Set (5)

Clearing a Set

• A set can be cleared of all its items, but still reserve its memory location by using the clear() function
  • this will empty the contents of a set and leave it empty, symbolised by the curly brackets ({}) or the set() constructor

setExample1 = {"4061CEM", "Programming", "Algorithms"}

setExample1.clear()

Modifying a Set (6)

Deleting a Set

• The entire set can be deleted and removed from the memory using the del keyword

setExample1 = {"4061CEM", "Programming", "Algorithms"}

del setExample1

Merging a Set (1)

• There are various methods of merging two sets together
  • update() and union()

Updating a Set

• The items of a set can be updated with the items of another set using the update() function

setExample1 = {"4061CEM", "Programming and Algorithms 1", "Dr Ian Cornelius"}
setExample2 = {"4059CEM", "Legal and Ethical Foundations", "Mr Terry Richards"}

setExample1.update(setExample2)

Merging a Set (2)

Unionising a Set

• The items of a set can be unionised with the items of another set using the union() function
  • this method will return a new set with both sets merged

setExample1 = {"4061CEM", "Programming and Algorithms 1", "Dr Ian Cornelius"}
setExample2 = {"4059CEM", "Legal and Ethical Foundations", "Mr Terry Richards"}

mergedSetExample1 = setExample1.union(setExample2)

Merging a Set (3)

Intersection of a Set i

• The items that only exist in both sets can be kept using the intersection_update() function
  • this will update the set it is called upon with only the duplicate values, removing any unique values

setExample1 = {"4061CEM", "Programming and Algorithms 1", "Dr Ian Cornelius"}
setExample2 = {"4059CEM", "Legal and Ethical Foundations", "Mr Terry Richards", "Dr Ian Cornelius"}

setExample1.intersection_update(setExample2)

Merging a Set (4)

Intersection of a Set ii

• The items that only exist in both sets can be kept using the intersection() function
  • this method will create a new set with only the duplicated values

setExample1 = {"4061CEM", "Programming and Algorithms 1", "Dr Ian Cornelius"}
setExample2 = {"4059CEM", "Legal and Ethical Foundations", "Mr Terry Richards", "Dr Ian Cornelius"}

mergedSetExample1 = setExample1.intersection(setExample2)

Merging a Set (5)

Symmetric Difference of a Set i

• The items that do not exist in both sets can be kept using the symmetric_difference_update() function
  • this will update the set it has been called upon with only the unique values, removing any duplicate values

setExample1 = {"4061CEM", "Programming and Algorithms 1", "Dr Ian Cornelius"}
setExample2 = {"4059CEM", "Legal and Ethical Foundations", "Mr Terry Richards", "Dr Ian Cornelius"}

setExample1.symmetric_difference_update(setExample2)

Merging a Set (6)

Symmetric Difference of a Set (ii)

• The items that do not exist in both sets can be kept using the symmetric_difference() function
  • this method will create a new set with only the unique values

setExample1 = {"4061CEM", "Programming and Algorithms 1", "Dr Ian Cornelius"}
setExample2 = {"4059CEM", "Legal and Ethical Foundations", "Mr Terry Richards", "Dr Ian Cornelius"}

mergedSetExample1 = setExample1.symmetric_difference(setExample2)

Copying a Set

• The method of copying a set by using set2 = set1 is incorrect
  • this method creates a reference to set1 and not an actual copy; therefore, any changes made in set1 will occur in set2
• The correct process of copying a set can be achieved by the copy() function or the set() constructor itself

setExample1 = {"4061CEM", "Programming and Algorithms 1", "Dr Ian Cornelius"}

copySetExample1 = setExample1.copy()
copySetExample2 = set(setExample1)