Hello
Technotizers, in this article we will be focusing on another Python specific
data type which is Sets. Sets
are used to store multiple items in a single variable. Set is one of 4 built-in
data types in Python used to store collections of data, the other 3 are Set, Tuple,
and Dictionary, all
with different qualities and usage. A set is a collection which is both unordered and unindexed.
Sets are created using curly brackets:
my_set = {'Mumbai','Delhi','Chennai','Kolkata'}
The output is obtained
as:
{'Kolkata',
'Delhi', 'Chennai', 'Mumbai'}
Some points to be remembered:
·
Set items
are unordered, unchangeable and do not allow duplicate values.
·
Set items
are not indexed.
·
A set item
can be of any data type like int, string or Boolean. A set can also contain
items of mixed data types.
Examples:
All the below given sets are valid in Python.
set2 = {1, 4, 24, 14, 8}
·
The set() constructor:
It is
another way of creating a set.
my_set = set(('Mumbai','Delhi','Chennai','Kolkata'))
So now let’s move forward!!
·
Accessing set elements:
Set
elements cannot be accessed using index, but they have to be accessed using for
loop or ask if a specified value is present in a set, by using
the in keyword.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
The
output is obtained as:
Kolkata Delhi Chennai Mumbai
True
·
Adding set elements:
Once a set is created, the items cannot
be changed but new items can be added. To add an item to the set, add() method
is used.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
city = city.add('Surat')
The
output is obtained as:
{'Chennai', 'Kolkata', 'Mumbai', 'Delhi', 'Surat'}
To add items from another set into the current set, use
the update() method.
city1 = {'Mumbai','Delhi','Chennai','Kolkata'}
print(city1)
The
output is obtained as:
{'Indore', 'Chennai', 'Nagpur', 'Kolkata', 'Mumbai', 'Delhi', 'Surat'}
The update() method does not have
to append only sets,
you can add any iterable object (tuples, sets, dictionaries etc.).
·
Remove set items:
The remove() or discard() methods
removes a specific item. If the item to remove does not exist, remove() will raise an
error. If the item to remove does not exist, discard() will NOT raise an
error.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
city.discard('Mumbai')
The
output is obtained as:
{'Kolkata', 'Chennai', 'Mumbai'}
{'Kolkata', 'Chennai'}
You can also use
the pop() method to remove an item, but this method will remove
the last item. Remember that sets are unordered, so you will
not know what item that gets removed. The return value of
the pop() method is the removed item.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
print(x)
The
output is obtained as:
Kolkata
{'Delhi', 'Chennai', 'Mumbai'}
The
‘del’ keyword entirely deletes the set.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
print(city)
#this
will raise an error because the set no longer exists
The clear() method clears the set. The set still exists but without any content.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
print(city)
The output is obtained as:
set()
The
output shows that the set is now empty.
·
Looping a set:
A for loop is used to loop through a set.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
The
output is obtained as:
Kolkata Delhi Chennai Mumbai
To know
more about for loops, refer the article Python-Loops
·
Join Sets:
There are
several ways to join two or more sets in Python. You can use the union() method
that returns a new set containing all items from both sets, or
the update() method that inserts all the items from one set into
another.
city = {'Mumbai','Delhi','Chennai','Kolkata'}
The
output is obtained as:
{98, 'Chennai', 5, 7, 12, 'Kolkata', 25, 'Mumbai', 'Delhi'}
Note: Both union() and update() will exclude any duplicate items.
The intersection_update() method will keep only
the items that are present in both sets.
city1 = {'Mumbai','Delhi','Chennai','Kolkata'}
print(city1)
The
output is obtained as:
{'Chennai', 'Mumbai'}
The intersection() method will return
a new set,
that only contains the items that are present in both sets.
city1 = {'Mumbai','Delhi','Chennai','Kolkata'}
The
output is obtained as:
{'Chennai', 'Mumbai'}
The symmetric_difference_update() method will keep only
the elements that are NOT present in both sets. And the symmetric_difference() method will return a
new set, that contains only the elements that are NOT present in both sets.
city1 = {'Mumbai','Delhi','Chennai','Kolkata'}
symmetric_difference_update(city2)
print(city1)
city1 = {'Mumbai','Delhi','Chennai','Kolkata'}
The
output is obtained as:
{'Kolkata', 'Delhi', 'Surat'}
{'Kolkata', 'Delhi', 'Surat'}
·
Set methods:
Python offers a bunch of set methods
given below:
|
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 |
With this we come to an end of this article. Hope it was helpful. Do provide your feedback and ideas through comments, it would be highly appreciated. See you soon!Keep coding and exploring new techs!!
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