Python is a versatile programming language that offers a wide range of data types to handle different kinds of information. One such data type is the mapping type. Mapping types in Python are used to store data in key-value pairs, where each key is unique and associated with a corresponding value.
Mapping types provide an efficient way to retrieve and manipulate data based on its unique identifier, which is the key. In Python, there are two main types of mapping data types: dictionaries and default dictionaries. Let’s explore each of them in detail.
Dictionaries
A dictionary is an unordered collection of key-value pairs enclosed within curly braces {}. The keys in a dictionary must be unique, immutable objects such as strings, numbers, or tuples. The values can be any object type, including other dictionaries.
To define a dictionary, you can use the following syntax:
my_dict = {'key1': 'value1', 'key2': 'value2', 'key3': 'value3'}
You can access the values stored in a dictionary using their corresponding keys. For example:
print(my_dict['key1']) # Output: value1
You can also modify the values associated with a specific key or add new key-value pairs to an existing dictionary. For instance:
my_dict['key2'] = 'new_value' # Modifying an existing value
my_dict['key4'] = 'new_key_value' # Adding a new key-value pair
Default Dictionaries
A default dictionary is a subclass of the built-in dictionary class that provides a default value for non-existing keys. This default value is specified when creating the default dictionary using either a default factory function or object.
To create a default dictionary, you can use the collections module, which provides a class named defaultdict. Here’s an example:
from collections import defaultdict
my_default_dict = defaultdict(int) # Default value is 0
In this example, the default value for non-existing keys is set to 0. You can use other built-in types such as list, set, or even custom functions as default values.
Default dictionaries are particularly useful when working with nested data structures or counting occurrences of elements. If a key does not exist in the dictionary, accessing it will return the default value instead of raising an error.
In Conclusion
In Python, mapping types like dictionaries and default dictionaries provide a flexible way to store and manipulate data in key-value pairs. Dictionaries are unordered collections of key-value pairs, while default dictionaries provide a default value for non-existing keys.
Remember that dictionaries have unique keys that allow quick retrieval of values based on their unique identifiers. Default dictionaries offer added flexibility by providing a default value for non-existing keys.
By understanding these mapping types and their capabilities, you can efficiently handle complex data structures and perform various operations in Python. So go ahead and experiment with these mapping types to make your Python programs more powerful and efficient!