are a fundamental data structure Python used to store - pairs. The "key" acts as a unique identifier, while the "value" can be any object or data type. Dictionaries are , meaning their contents can be changed after they are created. This allows for easy and modification of data within the dictionary.
One of the advantages of dictionaries is their ability to have and of different data types. For instance, a key can be a string, integer, or even a tuple. Similarly, a value can be a string, integer, list, or even another dictionary. This flexibility makes dictionaries versatile for a wide range of applications.
The "" of a dictionary refers to the number of key-value pairs it contains. You can obtain the length using the len() function. To update the value associated with a certain key, simply assign a new value to that key using the assignment operator (=).
In addition to accessing values using keys, dictionaries provide methods to retrieve all the keys or values as lists. The keys() method returns a list of all the keys, while the values() method returns a list of all the values. To obtain both keys and values simultaneously, the () method is useful. These methods allow for efficient traversal and manipulation of the dictionary contents.
The () method is used to remove all the key-value pairs from a dictionary, essentially emptying it. Alternatively, the () method can be used to remove a specific key-value pair and return its value. If a key does not exist, pop() can be called with a default value, ensuring the code does not raise a KeyError.
Dictionaries can be nested, meaning a dictionary can contain another dictionary as one of its values. This allows for the creation of hierarchical data structures. Accessing values in requires traversing through the keys of the outer dictionary and then the inner dictionary.
Under the hood, dictionaries in Python are implemented using a data structure. This enables quick lookup and retrieval of values based on their keys, even for large dictionaries. The key's hash value is used to determine its position in the hash table, ensuring efficient access.
Python provides various built-in methods to manipulate dictionaries. These include (), which allows safe retrieval of a value by key, ignoring the KeyError if the key is not found. The "in" keyword can be used to check if a key exists in the dictionary. To make an independent of a dictionary, the copy() method can be used.
is a concise way to create dictionaries in Python. It allows you to loop over an iterable and create a dictionary by specifying both the key and value in a single line of code. This feature is particularly useful when you want to transform or filter data from an existing iterable and store it as key-value pairs in a dictionary.
Keywords
in | dictionaries | nested dictionaries | value | get | values | items | clear | key | mutable | pop | dictionary comprehension | length | hash table | copy | keys | update |
