SET IN PYTHON

Set is used to represent group of immutable elements into a single entity. Set objects are mutable objects. Insertion order is not preserved. Duplicate elements are not allowed. On the top of the set objects, we can perform the mathematical set operations like union, intersection, symmetric difference and so on.

Example –

x=set()
print x
print type(x)
y=set([10,20,30])
print y
z={100,200,300,400,100,100}
print z

Output –

set([])

<type 'set'>

set([10, 20, 30])

set([200, 300, 400, 100])

Note – Set objects does not support indexing. Set allows heterogeneous elements.

 Example –

x={10,20,30}
print x
print x[1:2]
print x[0]
del x[1]

Output –

set([10, 20, 30])

Traceback (most recent call last):

  File "C:/Users/om/PycharmProjects/Pythonn/if3.py", line 3, in <module>

    print x[1:2]

TypeError: 'set' object has no attribute '__getitem__'

Example –

x={10,1.1,True,'rakesh',(20,30,40)}
print x
for p in x:
    print p

Output –

set([True, 10, 'rakesh', 1.1, (20, 30, 40)])

True

10

rakesh

1.1

(20, 30, 40)

Example –

x={10,20,30,40}
print x
x.add(50)
print x
x.update([30,60,70])
print x
x.update([80,50],[15,25,35,40])
print x
x.discard(30)
print x
x.remove(25)
print x

Output –

set([40, 10, 20, 30])

set([40, 10, 20, 50, 30])

set([70, 40, 10, 50, 20, 60, 30])

set([35, 70, 40, 10, 15, 80, 50, 20, 25, 60, 30])

set([35, 70, 40, 10, 15, 80, 50, 20, 25, 60])

set([35, 70, 40, 10, 15, 80, 50, 20, 60])

Note – In discard method, if the specified element is not present in Set then it doesn’t gives an error whereas in remove method it gives an error.

Example –

x=set('rakesh')
print x
print x.pop()
print x
x.clear()
print x
print len(x)

Output –

set(['a', 'e', 'h', 'k', 's', 'r'])

a

set(['e', 'h', 'k', 's', 'r'])

set([])

0

SET MATHEMATICAL OPERATIONS

Example –

A={1,2,3,4,5}
print A
B={4,5,6,7,8}
print B
print A|B
print A.union(B)
print A&B
print A.intersection(B)
print A-B
print A.difference(B)
print B-A
print B.difference(A)
print A^B
print A.symmetric_difference(B)

Output –

set([1, 2, 3, 4, 5])

set([8, 4, 5, 6, 7])

set([1, 2, 3, 4, 5, 6, 7, 8])

set([1, 2, 3, 4, 5, 6, 7, 8])

set([4, 5])

set([4, 5])

set([1, 2, 3])

set([1, 2, 3])

set([8, 6, 7])

set([8, 6, 7])

set([1, 2, 3, 6, 7, 8])

set([1, 2, 3, 6, 7, 8])

Example –

x=set('rakesh')
print x
print 'e' in x
print 'm' in x
for letter in set('apple'):
    print letter
for p in set(range(1,5)):
    print p

Output –

set(['a', 'e', 'h', 'k', 's', 'r'])

True

False

a

p

e

l

1

2

3

4

Example –

s={x for x in range(10)}
print s
t={y**2 for y in range(10)}
print t

Output –

set([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

set([0, 1, 4, 81, 64, 9, 16, 49, 25, 36])

PROGRAM TO ELIMINATE THE DUPLICATE ELEMENTS FROM 

LIST

x=[10,20,30,10,30,40]
print x
print set(x)

Output –

[10, 20, 30, 10, 30, 40]

set([40, 10, 20, 30])

OR

values=[5,5,1,1,2,3,4,4,5]
print values
output=[]
elim=set()
for value in values:
    if value not in elim:
        output.append(value)
        elim.add(value)
print output

Output –

[5, 5, 1, 1, 2, 3, 4, 4, 5]

[5, 1, 2, 3, 4]