Python

discard method in set

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discard method in set - Python

Discard method is used to delete or remove an element from a set.

This method takes exactly one argument.

When we call the discard method and pass an element as an argument Python will calculate the hash code of that element using the hash function.

This hash code is used to check whether an element is present in a set or not.

If an element is present with the same hash code it will be removed from the set.

If an element is not present in the set it will not give an error.

Syntax

set_name.discard(element)

Parameter –

element → element which you want to remove.

return value → none.

Example 1- Discard an element that is present in the set

				
					my_set={1,2,3,4}
print(my_set)
my_set.discard(3)
print(my_set)

# Output -
# {1,2,3,4} # my_set before removing element
# {1,2,4}   # my_set after removing element

In the above example, first we create a set (namely as my_set) with elements 1,2,3,4.

After that, we print the set in the output screen using the print() function.

After that, we discard element 3 from my_set using the discard method.

And then print modified set(my_set).

Example 2- Discard an element that does not exist in the set

				
					my_set=set()  # empty set
for i in range(1,6):
	my_set.add(i)
print(my_set)
my_set.discard(7)
print(my_set)

# Output -
# {1, 2, 3, 4, 5} # before removing element my_set
# {1, 2, 3, 4, 5} # after removing element my_set

In the above example, first we create an empty set(my_set) by using the set() function.

After that, we iterate a for-loop in the range 1-6 and add elements in my_set using the add() method.

After adding elements to the set we are trying to remove 7 from my_set that does not exist in it.

We can see that this line(line – 5) does not give any error.

Example 3- Discard even element from a set

				
					s={10,11,12,13,14,15,16,17,18,19}
s1={10,11,12,13,14,15,16,17,18,19}
print(s)
for i in s1:
	if i%2==0:
		s.discard(i)
print(s)

# Output -
# {10, 11, 12, 13, 14, 15, 16, 17, 18, 19} # before discard element from set s
# {11, 13, 15, 17, 19}                     # after discard element from set s

Example 4- Discard string from a set

				
					original_set={'hello','this', 'is', 'edSlash'}
print(original_set)
discarded_element=original_set.discard('hello')
print(discarded_element)
print(original_set) 

# Output -
# {'hello','this','is','edSlash'}
# None
# {'this', 'is', 'edSlash'}

In the above example, we can see that the discard method returns None.

Example 5- Discard method trying to pass two arguments

				
					s={'I','am','anurag', 'dubey'}
s.discard('anurag','dubey')
print(s)

# Output - 
# Traceback (most recent call last):
 #  File "/home/main.py", line 2, in <module>
    # s.discard('anurag','dubey')
# TypeError: set.discard() takes exactly one argument (2 given)

In the above example, we can see that we can pass only one argument to the discard method.

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