How Do I Add a New Key to a Python Dictionary?

Adding New Keys to Dictionaries

Dictionaries are a versatile data structure in programming, offering efficient storage and retrieval of key-value pairs. One common task when working with dictionaries is adding new keys and assigning values to them.

Question: How can I add a new key to an existing dictionary?

Answer:

Unlike other data structures, dictionaries do not have an explicit .add() method for adding new keys. Instead, adding a new key is achieved by assigning a value to that key.

For example:

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

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

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

If the specified key does not exist in the dictionary, Python will automatically create a new key and assign it the given value. On the other hand, if the key already exists, its value will be overwritten with the new value.

Therefore, to add a new key to an existing dictionary, simply use the assignment operator = to assign a value to the desired key. This method is straightforward and efficient, allowing for dynamic addition of new key-value pairs as needed.

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