Remove or delete an element from a set in Python

In Python, elements in a set can be removed by remove().

s = {'a', 'b', 'c'}

s.remove('a')

print(s)  # {'b', 'c'}

remove() returns None.

s = {'a', 'b', 'c'}

t = s.remove('a')

print(s)  # {'b', 'c'}
print(t)  # None

remove() takes one argument

s = {'a', 'b', 'c'}

s.remove('a', 'b')

# TypeError: remove() takes exactly one argument (2 given)

remove() can remove only one element.

A set can't be an argument of remove()

s = {'a', 'b', 'c'}

s.remove({'a', 'b'})

# KeyError: {'a', 'b'}

remove() can't remove a value that doesn't exist

s = {'a', 'b', 'c'}

s.remove('d')

# KeyError: 'd'

If trying to remove a value that isn't in a set, Python raises the KeyError exception. So you may want to check the existence before removing like this.

s = {'a', 'b', 'c'}

if 'a' in s:
    s.remove('a')

print(s)  # {'c', 'b'}

You may be happy to use discard()

s = {'a', 'b', 'c'}

s.discard('a')

print(s)  # {'b', 'c'}

discard() removes an element from a set like remove() and the difference of those is discard() doesn't raise the exception if the value doesn't exist.

s = {'a', 'b', 'c'}

s.discard('d')

print(s)  # {'b', 'a', 'c'}

Remove all the elements

s = {'a', 'b'}

print(id(s))  # 4517769280

s.clear()

print(s)  # set()
print(id(s))  # 4517769280

The clear() removes all the elements from the given set. The id of the set doesn't change by clearing.