The dict.pop() method in Python is used to remove a specified key from a dictionary and return its associated value. If the key does not exist in the dictionary and a default value is provided, it returns the default value; otherwise, it raises a KeyError. This method is useful when you want to remove a key-value pair while also obtaining the value of the removed key.

Syntax

value = dict.pop(key[, default])

• key: The key to be removed from the dictionary.
• default (optional): The value to return if the specified key does not exist in the dictionary. If not provided and the key is missing, a KeyError is raised.

Return Value

• The dict.pop() method returns the value associated with the specified key if it exists. If the key is not found and a default value is provided, it returns that default value. If the key is not found and no default value is given, it raises a KeyError.

Example

Here are some examples to illustrate how dict.pop() works:

1. Removing an Existing Key

# Example dictionary
my_dict = {'a': 1, 'b': 2, 'c': 3}

# Removing a key and getting its value
value_b = my_dict.pop('b')

print(value_b)  # Output: 2
print(my_dict)  # Output: {'a': 1, 'c': 3}

2. Attempting to Remove a Non-Existing Key Without Default

# Attempting to remove a key that does not exist
try:
    value_d = my_dict.pop('d')  # Key 'd' does not exist
except KeyError as e:
    print(e)  # Output: 'd'

3. Using a Default Value

# Using pop() with a default value for a non-existing key
value_d_default = my_dict.pop('d', 'Not Found')
print(value_d_default)  # Output: 'Not Found'
print(my_dict)          # Output: {'a': 1, 'c': 3}  # Dictionary remains unchanged

Use Cases

• Removing Items: Useful for removing items from a dictionary when you need to process the value while deleting the key.
• Handling Missing Keys: The optional default value allows you to handle cases where a key might not exist without raising an error.
• Stack Operations: Can be used in data structures that require LIFO (Last In, First Out) behavior by popping the most recently added item.

Summary

The dict.pop(key[, default]) method is a convenient way to remove a key-value pair from a dictionary in Python while returning the associated value. It provides a safe way to handle potential missing keys with the option to specify a default return value, making it an essential method for dictionary manipulation.