Python set is an un-ordered and un-indexed collection of elements.
- Every element is unique.
- The set contains elements that are un-ordered.
- No duplicates are allowed.
- The set itself is mutable i.e. one can add/remove items(elements) from it.
- Unlike arrays, wherein the elements are stored in order, the order of elements in a set is not defined.
- The elements in the set are not stored in their order of appearance in the set.
Table of Contents
Creation of Sets in Python
Set can be created by placing all the elements within curly braces {}, separated by a comma. They can also be created by using the built-in function set().
The elements can be of different data types, but a Set doesn’t support mutable elements. Sets are unordered, so one can’t be sure of the order of elements in which they will appear.
Example: Creation of Sets
Days=set(["Mon","Tue","Wed","Thu","Fri","Sat","Sun"])
Fruits = {"apple", "banana", "cherry"}
Name=set('Quit')
print(Name)
print(Fruits)
print(Days)
Output:
{‘u’, ‘Q’, ‘i’, ‘t’}
{‘cherry’, ‘banana’, ‘apple’}
{‘Sun’, ‘Wed’, ‘Mon’, ‘Thu’, ‘Tue’, ‘Sat’, ‘Fri’}
Recommended Readings:
Access elements from the Python Set
Since, sets are un-ordered and un-indexed, one cannot access the elements by referring to its index, unlike arrays.
The elements of the Sets can be accessed by either of the following ways:
- Iterate through the loop of the set items using a
forloop . - Check whether a specified value is present in a set, by using the
inkeyword .
Example: Accessing elements from a Set
Fruits = {"apple", "mango", "cherry"}
for a in Fruits:
print(a)
print("banana" in Fruits)
print("mango" in Fruits)
Output:
mango
cherry
apple
False
True
Add elements to a Python Set
We can add elements to a set by using add() function. In case, we require to add more elements we need to use update() method to do so.
Example: Addition of elements to a Set
Fruits = {"apple", "mango", "cherry"}
Fruits.add("grapes")
print(Fruits)
Fruits.update(["banana", "orange", "strawberry"])
print(Fruits)
Output:
{‘cherry’, ‘apple’, ‘mango’, ‘grapes’}
{‘strawberry’, ‘cherry’, ‘apple’, ‘orange’, ‘banana’, ‘mango’, ‘grapes’}
Removal of elements from a Set
We can delete the items from the Set using either of the following methods:
- By using
remove()method - By using
discard()method - By using
clear()method – deletes all the elements from the Set - By using
del()method – deletes the entire Set
Example 1: Using remove() method
Fruits = {"apple", "grapes", "cherry"}
Fruits.remove("grapes")
print(Fruits)
Output:
{‘cherry’, ‘apple’}
Example 2: Using discard() method
Fruits = {"apple", "grapes", "cherry"}
Fruits.discard("grapes")
print(Fruits)
Output:
{‘cherry’, ‘apple’}
Example 3: Using clear() method
Fruits = {"apple", "grapes", "cherry"}
Fruits.clear()
print(Fruits)
Output:
set()
Example 4: Using del() method
Fruits = {"apple", "grapes", "cherry"}
del Fruits
print(Fruits)
Output:
Traceback (most recent call last):
File "main.py", line 5, in <module>
print(Fruits)
NameError: name 'Fruits' is not defined
Methods in Sets
| Method | Description |
|---|---|
| add() | Adds an element to the set |
| clear() | Removes all the elements from the set |
| copy() | Returns a copy of the set |
| difference() | Returns a set containing the difference between two or more sets |
| difference_update() | Removes the items in this set that are also included in another, specified set |
| discard() | Remove the specified item |
| intersection() | Returns a set, that is the intersection of two other sets |
| intersection_update() | Removes the items in this set that are not present in other, specified set(s) |
| isdisjoint() | Returns whether two sets have a intersection or not |
| issubset() | Returns whether another set contains this set or not |
| issuperset() | Returns whether this set contains another set or not |
| pop() | Removes an element from the set |
| remove() | Removes the specified element |
| symmetric_difference() | Returns a set with the symmetric differences of two sets |
| symmetric_difference_update() | inserts the symmetric differences from this set and another |
| union() | Return a set containing the union of sets |
| update() | Update the set with the union of this set and others |
Set Operations in Python
Sets are used to carry out mathematical functionality set operations such as union, difference, intersection, and symmetric difference.
Set Union – Inclusion of all elements from both the sets.
Union operation is performed by either of the following methods:
- By using
|operator - By using
union()method
Example: Union of Sets
X = {1, 2, 3}
Y = {6, 7, 8}
print(X | Y)
print(Y.union(X))
Output:
{1, 2, 3, 6, 7, 8}
{1, 2, 3, 6, 7, 8}
Set Intersection – Inclusion of elements that are common to both the sets.
Intersection operation is performed by either of the following methods:
- By using
&operator - By using
intersection() method
Example: Intersection of Sets
X = {1, 2, 3}
Y = {3, 2, 8}
print(X & Y)
print(Y.intersection(X))
Output:
{2, 3}
{2, 3}
Set Difference – Inclusion of elements from either of the sets.
(A – B) contains the elements that are only in set A but not in set B.
(B – A) contains the elements that are only in set B but not in set A.
Difference operation is performed by either of the following methods:
- By using
-operator - By using
difference()method
Example: Difference of Sets
X = {1, 2, 3}
Y = {3, 2, 8}
print(X - Y)
print(Y.difference(X))
Output:
{1}
{8}
Set Symmetric Difference – Inclusion of elements from both the sets except the common elements of the sets
Symmetric Difference operation is performed by either of the following methods:
- By using
^operator - By using
symmetric_difference()method
Example: Symmetric Difference of Sets
X = {1, 2, 3, 9, 0}
Y = {3, 2, 8, 7, 5}
print(X ^ Y)
print(Y.symmetric_difference(X))
Output:
{0, 1, 5, 7, 8, 9}
{0, 1, 5, 7, 8, 9}