Python - Sets

To check if an element is present in a set in Python, you can use the in keyword. Here's an example:

# Creating a set
my_set = {1, 2, 3, 4, 5}

# Checking if an element is present in the set
element_to_check = 3

if element_to_check in my_set:
    print(f"{element_to_check} is present in the set.")
else:
    print(f"{element_to_check} is not present in the set.")

3 is present in the set.

In this example, we create a set my_set and check if element_to_check (which is 3) is present in the set using the in keyword.

The discard() and remove() methods are used to remove elements from a set in Python. The key difference between them is that if the element is not present in the set, discard() does nothing, while remove() raises a KeyError.

Here's an example demonstrating their use:

# Creating a set
my_set = {1, 2, 3, 4, 5}

# Using discard() to remove an element
my_set.discard(3)
print("After using discard(3):", my_set)

# Using remove() to remove an element
try:
    my_set.remove(4)
    print("After using remove(4):", my_set)
except KeyError as e:
    print(f"KeyError: {e}")
    
# Attempting to remove a non-existent element with discard()
my_set.discard(6)
print("After using discard(6):", my_set)

# Attempting to remove a non-existent element with remove() (raises KeyError)
try:
    my_set.remove(6)
    print("After using remove(6):", my_set)
except KeyError as e:
    print(f"KeyError: {e}")

After using discard(3): {1, 2, 4, 5}
After using remove(4): {1, 2, 5}
After using discard(6): {1, 2, 5}
KeyError: 6

In this example, we create a set my_set and use discard() and remove() to remove elements. Note that discard() does not raise an error when attempting to remove a non-existent element, while remove() raises a KeyError.

The clear() method in Python sets is used to remove all elements from the set, resulting in an empty set.

Here's an example demonstrating the use of clear():

# Creating a set
my_set = {1, 2, 3, 4, 5}

# Displaying the set before using clear()
print("Before using clear():", my_set)

# Using clear() to remove all elements
my_set.clear()

# Displaying the set after using clear()
print("After using clear():", my_set)

Before using clear(): {1, 2, 3, 4, 5}
After using clear(): set()

In this example, we create a set my_set and use the clear() method to remove all elements from the set, resulting in an empty set.

The copy() method in Python sets is used to create a shallow copy of the set. A shallow copy creates a new set, but the elements themselves are still references to the same objects as the original set.

Here's an example demonstrating the use of copy() to create a shallow copy of a set:

# Creating a set
original_set = {1, 2, 3, 4, 5}

# Creating a shallow copy using copy()
shallow_copy_set = original_set.copy()

# Displaying both sets
print("Original set:", original_set)
print("Shallow copy set:", shallow_copy_set)

Original set: {1, 2, 3, 4, 5}
Shallow copy set: {1, 2, 3, 4, 5}

In this example, copy() is used to create a shallow copy of original_set, resulting in a new set shallow_copy_set. Both sets have the same elements, and modifying the elements in one set does not affect the other.