Python are data structures that store - pairs. A key is a unique identifier, while a value is the associated data. They are , meaning that their contents can be modified after creation. Conversely, are and cannot be changed. The of a dictionary corresponds to the number of keys it contains.
To a value in a dictionary, we can use the key to access the corresponding item and assign a new value to it. This operation is particularly useful when dealing with mutable data types stored as dictionary .
To retrieve all the keys or values from a dictionary, we can use the keys() and values() methods, respectively. Additionally, we can a list of key-value pairs using the () method.
If we want to remove all the items from a dictionary, we can use the () method. On the other hand, if we wish to remove a specific key-value pair, we can use the () method, providing the key as an argument.
Dictionaries can even be nested within each other, allowing for more complex data structures. This is referred to as . They can be useful for organizing and accessing data in a more structured manner.
Behind the scenes, dictionaries utilize a implementation, which allows for efficient key-value retrieval. The keys are hashed to their corresponding indices in the underlying array, which results in constant-time complexity for most dictionary operations.
Python provides a wide range of to perform various operations. In addition to the mentioned ones, we have methods like get(), which allows us to retrieve a value for a given key, and in, which can be used to check if a key exists in the dictionary.
When working with dictionaries, it is important to note that assigning one dictionary to another creates a reference, not a . To make an independent copy, we can use the copy() method.
Python also offers a concise way to create dictionaries using . Similar to list comprehension, we can specify the key-value pairs within curly braces and iterate over an iterable to populate the dictionary. This can be a powerful and efficient way to construct dictionaries based on certain conditions or transformations.
