Python Sets

What are Sets?

Sets are used to store multiple items in a single variable.

  myset = {"bigsmoke", "isnt", "hacker"}

A set is a collection which is unordered and unindexed and do not allow duplicate values.

len()

We can use the function len(set1) to find the length of set.

  set1 = {"bigsmoke", "hulk", "thor"}
  print(len(set1))
  #4

Access Set Items (using loops)

We can’t use indexing in sets to access a item. But we can use for loop to do this.

  set1 = {"bigsmoke", "hulk", "thor"}
  for i in set1:
      print(i)

add()

To add one item to a set use the add() method.

  set1 = {"bigsmoke", "hulk", "thor"}
  set1.add("iron man")
  print(set1)
  # OUTPUT
  # {"bigsmoke", "hulk", "thor", "iron man"}

  set1 = {"bigsmoke", "hulk", "thor"}
  set2 = {"batman", "superman", "joker"}

  set3 = set1.update(set2)
  print(set3)

  set1 = {"bigsmoke", "hulk", "thor"}
  set1.remove("bigsmoke")
  print(set1)

Delete an Entire Set

The del keyword will delete the set completely.

  set1 = {"bigsmoke", "hulk", "thor"}
  del set1
  print(set1)
  # You will get an error while running this function as "set1" is not defined

Clear an Entire Set

The clear() function will clear all the elements present in the set.

  set1 = {"bigsmoke", "hulk", "thor"}
  set1.clear()
  print(set1)

Copy of a set

The copy() function will copy all the elements from one set to another.

  set1 = {"bigsmoke", "hulk", "thor"}
  set2 = set1.copy()
  print(set2)

Difference between two sets

The difference() function returns a set containing the difference between two or more sets.

  set1 = {apple, banana, mango}
  set2 = {microsoft, apple, oneplus}
  set3 = set1.difference(set2)
  print(set3)

Printing single time appeared in both sets

The difference_update() removes the items in this set that are also included in another, specified set.

  set1 = {"apple", "banana", "mango"}
  set2 = {"microsoft", "apple", "oneplus"}
  set3 = set1.difference_update(set2)
  print(set3)

Removing the specified item

The discard() function removes the specified item

  fruits = {"apple", "banana", "cherry"}
  fruits.discard("banana")
  print(fruits)
  # {"apple", "cherry"}

Printing the intersection of two or more sets

The intersection() function returns a set, that is the intersection of two or more sets

  x = {"apple", "banana", "cherry"}
  y = {"google", "microsoft", "apple"}
  z = x.intersection(y)
  print(z)
  # {"apple"}

Removing item that is not present in both sets

The intersection_update() function removes the items in this set that are not present in other, specified set(s)

  x = {"apple", "banana", "cherry"}
  y = {"google", "microsoft", "apple"}
  x.intersection_update(y)
  print(x)
  # As apple is common in both sets
  # {"apple"}

Intersection of two sets possible or not

The isdisjoint() function returns whether two sets have an intersection or not

  x = {"apple", "banana", "cherry"}
  y = {"google", "microsoft", "facebook"}
  z = x.isdisjoint(y)
  print(z)
  # Returns True if no common/same value is present in both sets.
  # True

To check whether set1 is present in set2

The issubset() function returns whether another set contains this set or not

  x = {"a", "b", "c"}
  y = {"f", "e", "d", "c", "b", "a"}
  z = x.issubset(y)
  print(z)
  # Returns True if x set is present in y set
  # True

To check whether set2 is present in set1

The issuperset() function returns whether set 1 contains set 2 or not

  x = {"f", "e", "d", "c", "b", "a"}
  y = {"a", "b", "c"}
  z = x.issuperset(y)
  print(z)
  # Return True if set y is present in set x
  # True

Removing an element from the set

The pop() function removes a random element from the set

  fruits = {"apple", "banana", "cherry"}
  fruits.pop()
  print(fruits)
  # It can remove random element so you can't say any specific value

Removing a specific element from the set

The remove() function removes the specified element

  fruits = {"apple", "banana", "cherry"}
  fruits.remove("banana")
  print(fruits)
  # Removes banana from the set
  # {"apple", "cherry"}

To find symmetric difference between two sets

The symmetric_difference() function returns a set with the symmetric differences of two sets

  x = {"apple", "banana", "cherry"}
  y = {"google", "microsoft", "apple"}
  z = x.symmetric_difference(y)
  print(z)
  # It returns values that are different in both sets
  # {"banana", "cherry", "google", "microsoft"}

To insert symmetric difference elements from both sets

The symmetric_difference_update() function inserts the symmetric differences from this set and another

  x = {"apple", "banana", "cherry"}
  y = {"google", "microsoft", "apple"}
  x.symmetric_difference_update(y)
  print(x)
  # It functions same as symmetric_difference() function
  # {"banana", "google", "cherry", "microsoft"}

To add elements from both sets

The union() function returns a set, containing the union of sets

  set1 = {"bigsmoke", "hulk", "thor"}
  set2 = {"batman", "superman", "joker"}

  set3 = set1.union(set2)
  print(set3)
  # It unifies both the sets
  #{"bigsmoke", "hulk", "thor", "batman", "superman", "joker"}

Updating set with another set

The update() function updates the set with another set, or any other iterable

  x = {"apple", "banana", "cherry"}
  y = {"google", "microsoft", "apple"}
  x.update(y)
  print(x)
  # It combines two sets into one
  # {"apple", "banana", "cherry", "google", "microsoft"}