Dictionaries are a fundamental data structure in Python that allows you to store and manipulate collections of key/value pairs effectively. Unlike lists, which are ordered and indexed by numbers, dictionaries provide a way to map arbitrary keys to their corresponding values.

Creating a Dictionary

To create a dictionary, you can use curly braces {} and separate each key/value pair with a colon :. Here’s an example with a single key/value pair:

dog = { 'name': 'Roger' }

In this example, the key is 'name', and the corresponding value is 'Roger'.

Accessing and Modifying Values

You can access the values in a dictionary by using the key inside square brackets. For example:

dog['name']  # Output: 'Roger'

You can also modify the value associated with a specific key by assigning a new value to it:

dog['name'] = 'Syd'

Additional Dictionary Operations

Apart from accessing and modifying values, dictionaries offer several other useful methods and operations:

get() Method

The get() method allows you to retrieve the value of a key while providing a default value if the key doesn’t exist:

dog.get('name')           # Output: 'Roger'
dog.get('test', 'default')  # Output: 'default'

pop() Method

The pop() method retrieves the value of a key and removes the key/value pair from the dictionary:

dog.pop('name')           # Output: 'Roger'

popitem() Method

The popitem() method retrieves and removes the last key/value pair inserted into the dictionary:

dog.popitem()

in Operator

You can check if a key is present in a dictionary using the in operator:

'name' in dog  # Output: True

keys(), values(), and items() Methods

These methods allow you to retrieve the keys, values, and key/value pairs of a dictionary, respectively:

list(dog.keys())       # Output: ['name', 'age']
list(dog.values())     # Output: ['Roger', 8]
list(dog.items())      # Output: [('name', 'Roger'), ('age', 8)]

len() Function

The len() function can be used to get the number of key/value pairs in a dictionary:

len(dog)  # Output: 2

Adding and Removing Key/Value Pairs

You can add a new key/value pair to a dictionary by assigning a value to a new key:

dog['favorite food'] = 'Meat'

To remove a specific key/value pair from a dictionary, you can use the del statement:

del dog['favorite food']

Copying a Dictionary

To create a copy of a dictionary, you can use the copy() method:

dogCopy = dog.copy()

Conclusion

Dictionaries are a powerful data structure in Python that allow you to store and manipulate key/value pairs efficiently. Understanding how to create, access, and modify dictionaries, as well as the various methods available, can greatly enhance your Python programming skills.