Sets in the python programming language.ppt

SETS
Vinay Agrawal
Asst. Professor
CEA Dept.
GLA University,
Mathura

Sets
• Set is another data structure supported by Python.
• It is Mutable.
• It is unordered.
• Does not have the concept of indexing.
• No meaning of duplicate elements.
• Symbol used for representing set is { }
For example, s={1,2,3}

Q1. How we can create empty set in Python?
ANS. S=set()
S={} will not create empty set. It will create empty
dictionary.

Sets are Mutable
We can add elements in set by using following
methods:-
1. s.add(element):- This will add one element at a time
in the set s
s={1,2,3}
s.add(10)
print(s)
O/P:- {1,2,3,10}
Elements may be in any order

2. s1.update(s2):- This will add one or more than one
element at a time in a set.
s1={1,2,3}
s2={88,67} # or s2=[88,67] or s2=(88,67)
s1.update(s2)
print(s1)
O/P:- {1,2,3,88,67}
Elements may be
in any order

For deletion, we are having different methods:-
1. s.pop():- This will delete arbitrary element from the given set s
s={4,5,6}
s.pop()
print(s)
O/P: -{4,6} or {4,5} or {5,6}
2. s.remove(element):- This will delete the specified element.
s={4,5,6}
s.remove(4)
print(s)
O/P:- {5,6}

3. s.discard(element):- It is similar to remove method. The
difference lies when the specified element is not present
in the set.
s.discard(element) does not raises an error
when element is not there while s.remove(element)
raises an error
s={1,2,3}
s.discard(4)
print(s)
O/P:- {1,2,3}

4. s.clear():- This will empties the set
s={1,2,3}
s.clear()
print(s)
O/P:- set()

Other methods
 s.intersection_update(t)
 s.difference_update(t)
 s.symmetric_difference_update(t)
 s.isdisjoint(t)

Functions for sets
 max(s)
 min(s)
 sum(s)
 sorted(s)- It will return a list of sorted elements

What is s1 ?
S1=set(“My name is Piyush and Piyush is My name”.split())
print(S1)
ANS. {“My”, ”name”, ”is”, ”Piyush”, ”and”}

 The elements of sets must be immutable but set itself
is mutable.
s1={1,2,3,4} Right
s2={1,2,3,(4,5)} Right
s3={1,2,3,[4,5]} Wrong
s4={1,2,3,”Hello”} Right

Is there any error?
1. s={10,45,63,56}
print(s[0])
2. s={10,45,63,56}
s[1]=500
3. s={4,5,[100,200]}
print(s)
4. s={1,2,3,4}
print(s[0:2])

Iterating a Set
S={45,65,89,100}
for i in S:
print(i)

Programs
1. Write a Program that generates a set s1 of 10
even numbers and another set s2, of 10 odd
numbers
2. Write a Program that generates a set s1 of prime
numbers from 100 to 999 and another set s2, of
Armstrong numbers from 100 to 999.
3. Do the operation of union, intersection, difference,
symmetric difference of sets s1 and s2(refer
Program 1)

4.Do the operation of union, intersection, difference,
symmetric difference of sets s1 and s2(refer
Program 2)
5. Write a Program that creates two sets(s1 and s2)
that stores squares and cubes of numbers from 1 to
10 respectively. Now Demonstrate the use of
update(), pop(), remove(), add() and clear()

6. Write a Program that creates two sets. One of
even numbers in range 1-10 and other has all
composite numbers in range 1-20. Demonstrate use
of issuperset(), len() and sum() functions on the sets.
7. Write a Program that has a list of countries. Create
a set of the countries and print the names of the
countries in sorted order.

frozenset
Set is mutable while frozenset is immutable.
s={1,2,3,4,5}
fs=frozenset(s)
print(fs)

s={1,2}
fs=frozenset(s)
s.add(100) #Right # fs.add(100) wrong
s.update((4,5)) #Right # fs.update((4,5)) wrong
s.remove(2) #Right # fs.remove(2) wrong
s.discard(1) #Right # fs.discard(1) wrong
s.pop() #Right # fs.pop() wrong
s.clear() #Right #fs.clear() wrong

Sets in the python programming language.ppt

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