How Do I Add New Keys to a Python Dictionary?

Adding New Keys to a Dictionary

In Python, dictionaries are mutable and allow for the addition and deletion of key-value pairs. Unlike conventional data structures that offer an explicit .add() method, dictionaries handle key creation and assignment differently.

Solution

To add a new key to an existing dictionary, simply assign a value to the key:

d = {'key': 'value'}
print(d)  # {'key': 'value'}

# Add a new key
d['mynewkey'] = 'mynewvalue'

print(d)  # {'key': 'value', 'mynewkey': 'mynewvalue'}

This operation has two outcomes:

• If the key doesn't exist, it's created and assigned the provided value.
• If the key already exists, its current value is overwritten with the new value.

Example

Consider the following code:

user_data = {'name': 'John Doe', 'age': 30}
print(user_data)  # {'name': 'John Doe', 'age': 30}

# Add a new key to the dictionary
user_data['email'] = 'john.doe@example.com'

print(user_data)  # {'name': 'John Doe', 'age': 30, 'email': 'john.doe@example.com'}

In this example, a new key 'email' is added to the 'user_data' dictionary, and it points to the value 'john.doe@example.com'.

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