Python Ninja Bootcamp 11-Set

Learn Python like a Professional! Take You from 0 to Hero

In this Python lecture, we will learn about the Set.

"Set is an unordered collection of unique(no duplicate) and immutable items".

Let's look at Set example-

Create Set

Set is defined by placing all the elements inside curly braces { }, separated by comma or by using the built-in function set( ).

s={1,2,3,4,5}

print(s)

>> { 1,2,3,4,5 }

Another method of Creating Set

We have built-in set( ) function to create a set.

s= set() # create a empty set

print(s)

>> set( )

We can add a single element using the add( ) method.
And multiple elements using the update( ) method.

# set can hold different object type (integer, float, string etc)
s.add(1) # add an element to the set

s.add(1.2) # 1.2 is added in the set

s.add('string') # 'string' is added in the set

print(s)

>> {1, 'string', 1.2}

Notice element may appear in a different order then the order followed while adding the element

We can update the set with the union of list, tuple & set

s.update( [3,4,5] , ('three','four') , {'five',2} )

print(s)

>> { 1, 'string', 3, 4, 1.2, 5, 'four', 2, 'five', 'three' }

# Try to add the same element

s.add(1)

print(1)

>> { 1, 'string', 3, 4, 1.2, 5, 'four', 2, 'five', 'three' }

Notice element 1 is not added again. This happened because a set is the collection of a unique element.

We can cast a list with multiple repeated elements to the set to get the unique elements.

l=[1,1,2,2,3,3,3,4,4,4,4]


print( l )

>> [1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4]

#cast as set to get unique element

print(set(l))

>> {1,2,3,4}

.
Remove the element from the set

# we have a given set

s={1,2,3,4,5}

print(s)

>> {1,2,3,4,5}

s.remove(1) # remove an element from set

print(s)

>> {2,3,4,5}

Now try to remove 1 again from the set s

s.remove(1)

>> keyError: 1

Notice remove( ) method returns error on removing non-existing element.

We have discard() method to remove an element. If the item does not exist in the set, it remains unchanged.

s.discard(2)

print(s)

>> {3,4,5}

Again try to remove 2.

s.discard(2)

print(s)

>> {3,4,5}

print(s.pop()) # remove and return an arbitrary element

>> 3

print(s)

>> {4,5}

s.clear(2) # remove the all the element from set

print(s)

>> set( )

Set Operation

Let's create the two sets:

#Create a even set between 0 t0 10

even={ 2,4,6,8,10 }

print(even)

>> {2,4,6,8,10}

#Create a prime set between 0 t0 10

prime={ 2,3,5,7 }

print(prime)

>> {2,3,5,7 }

1. Union

Union of even and prime is a set of all elements from both sets

In Python, union is performed by using union() method.

even.union(prime) # return the union of sets

>> {2, 3, 4, 5, 6, 7, 8, 10}

2. Intersection

Intersection of even and prime is a set of common elements from both sets.

In Python, intersection is performed by using intersection() method

even.intersection(prime)  # return the intersection of sets

>> {2}

3. Difference

Difference of even and prime is a set of all elements in the even set but not the prime set.

In Python, difference is performed by using difference( ).

even.difference(prime) # return the difference of two or more set

>> {4, 6, 8, 10}

EDITS ARE WELCOMED!!

In the next Blog, we will discuss Boolean.

https://sngurukuls247.blogspot.com/2018/09/python-ninja-bootcamp-12-boolean.html

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