Sets

• Sets is a group of unique values.

• Duplicates are not allowed
• Set is a mutable and an unordered collection of items.
• Indexing and slicing not allowed for the set.
• Represents set elements within curly brackets {}, separated by comma, or by using the
built-in set() function.
Creating a set:
Set can have any number of items and they may be of different types (integer, float, tuple,
string etc.). But a set cannot have mutable elements like lists or dictionaries as its elements.
Syntax:
Set_variable = {val1, val2, ….}
Example: Different types of sets in python
s = {3, 8, 6} # set of integers
print(s) # Output: {8, 3, 6}
s = {4,'abc',78.5, (4,8,9)} # set of mixed datatypes
print(s) # Output: {(4, 8, 9), 78.5, 4, 'abc'}
s = {5,1,7,9,5,6,5} # set cannot have duplicates
print(s) # Output: {1, 5, 6, 7, 9}
s = set([3,8,0,7])
print(s) # Output: {8, 0, 3, 7}
s = {5, 7, [7, 2]} # set cannot have mutable items
print(s) # Output: TypeError: unhashable type: 'list'
Note: Empty curly braces {} will make an empty dictionary in Python. To make a set without any
elements, we use the set() function without any argument.
a = {}
print(type(a))
print(a)
a = set()
print(type(a))
print(a)

Frozen set:
• A frozen set in python is a set whose values cannot be modified.
• Frozen sets can be created using the frozenset() method.
Example:
a = {1,'a',4,9.5}
b = frozenset(a)
print(b)
Output: frozenset({1, 4, 'a', 9.5})

b.add(7)
print(b)
Output: AttributeError: 'frozenset' object has no attribute 'add'

Accessing elements of a set:

• Set elements cannot be accessed using the index numbers.
• You can access the elements of a set by looping through it.
Example:
my_set = {1,'a',4,9.5}
for x in my_set:
print(x)
Output: 1
4
a
9.5

Set Operations:
Function Description Example
add() Add a single element s = {5,9,0}
using the add() method. s.add(7)
Dduplicates are avoided print(s) #Output: {0, 9, 5, 7}
update() Add a multiple elements s = {5,9,0}
using the update() method. s.update([7,8,5,10])
The update() method can print(s) # Output: {0, 5, 7, 8, 9, 10}
take tuples, lists, strings or s.update([8,3], {1,6,8}) # add list &
other sets as its argument. set
Duplicates are avoided. print(s) # Output: {0, 1, 3, 5, 6, 7, 8,
9, 10}
remove() Remove a particular s = {5,9,0,'abc','def'}
element from a set. s.remove('abc')
Returns KeyError if print(s) # Output: {0, 5, 'def',
element is not present. 9}
s.remove(10)
print(s) # Output: KeyError:
10
discard() Same as remove() but s = {5,9,0,'abc','def'}
does not give an error if s.discard('abc')
element is not present in print(s) # Output: {0, 5, 'def',
the set. 9}
s.discard(10)
print(s) # Output: {0,5,’def’,9}
pop() Removes and returns any my_set = {1,'a',4,9.5}
arbitrary element from my_set.pop()
set. KeyError is raised if print(my_set) # Output: {4, 'a',
set is empty. 9.5}
clear() Removes all elements my_set = {1,'a',4,9.5}
from the set. my_set.clear()
print(my_set) # Output: set()
union() Return all the elements a = {1,'a',4,9.5}
from both the set. b = {10,20}
Union is also performed print(a|b) # Output: {1, 4, 'a', 9.5,
using “ | “ operator. 10, 20}
print(a.union(b)) #Output: {1, 4, 'a',
9.5, 10, 20}
intersection() or “&” Returns a new set that a = {1,'a',4,9.5}
has elements which are b = {1,10,20}
common in both the sets. print(a&b) # Output: {1}
print(a.intersection(b)) # Output: {1}
difference() or “-“ Returns a new set that a = {1,'a',4,9.5}
has elements in set a but b = {1,10,20}
not in set b. print(a-b) # Output: {9.5, 4,
'a'}
print(a.difference(b)) # Output: {9.5,
4, 'a'}
symmetric_difference() Returns a new set with a = {1,'a',4,9.5}
or “^” elements either in a or in b = {1,10,20}
b but not both. print(a^b) # Output: {4,9.5,10,'a',20}
print(a.symmetric_difference(b)) #
Output: {4,9.5,10,'a',20}
issubset() or “<=” Returns true if every a={4,7,9,'def',(3,'g')}
element in set a is present b={6,9,4,7,'def',(3,'g')}
in set b and false print(a.issubset(b)) # Output: True
otherwise. print(a<=b) # Output: True

issuperset() or “s>=t” Returns true if every a={4,7,9,'def',(3,'g')}

element in b is present in b={6,9,4,7,'def',(3,'g')}
set a and false otherwise. print(a.issuperset(b)) # Output: True
print(a>=b) # Output: True
isdisjoint() Returns true if two sets a={4,7,9}
have a null intersection. b={3,5,8}
print(a.isdisjoint(b)) # Output: True
copy() Returns a copy of set a={4,7,9}
b=a.copy()
print(b) # Output: {9, 4, 7}
all() Returns true if all s = {3,9,1,4,0}
elements in the set are print(all(s)) # Output: False
True and False
otherwise.
any() Returns true if any of the s = {3,9,1,4,0}
elements in the set is true. print(any(s)) # Output: True
Returns false if the set is
empty.
enumerate() Returns an enumerate s = {3,9,1,4,0,'ab','ac'}
object which contains for i in enumerate(s):
index as well as value of print(i, end=" ")
all the items of set as a
pair. Output: (0, 0) (1, 1) (2, 'ab') (3, 3) (4,
4) (5, 9) (6, 'ac')