1. Introduction
A dictionary, also known as dict, is a built-in Python data type that represents a collection of key-value pairs. It is one of the most commonly used data types in Python programming due to its versatility and efficiency in storing and retrieving data. In this article, we will explore the various aspects of dictionaries in Python 3.
2. Creating a Dictionary
To create a dictionary in Python, you can use the curly braces {} or the built-in dict() function. Each key-value pair is separated by a colon (:), and multiple pairs are separated by a comma (,). Here's an example:
my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
print(my_dict)
This code creates a dictionary named my_dict with three key-value pairs: 'name' with value 'John', 'age' with value 25, and 'city' with value 'New York'. The output of the print statement will be:
{'name': 'John', 'age': 25, 'city': 'New York'}
2.1 Accessing Dictionary Values
To access the values in a dictionary, you can use square brackets [] and the key name. Here's an example:
print(my_dict['name'])
print(my_dict['age'])
print(my_dict['city'])
The above code will print:
John
25
New York
3. Modifying Dictionary Values
You can modify the values in a dictionary by assigning a new value to a specific key. Here's an example:
my_dict['age'] = 30
print(my_dict)
The output will be:
{'name': 'John', 'age': 30, 'city': 'New York'}
4. Dictionary Methods
4.1 keys() Method
The keys() method returns a list of all the keys in a dictionary. Here's an example:
print(my_dict.keys())
The output will be:
['name', 'age', 'city']
You can also use the list() function to convert the result into a list explicitly:
print(list(my_dict.keys()))
4.2 values() Method
The values() method returns a list of all the values in a dictionary. Here's an example:
print(my_dict.values())
The output will be:
['John', 30, 'New York']
4.3 items() Method
The items() method returns a list of all the key-value pairs in a dictionary, where each pair is represented as a tuple. Here's an example:
print(my_dict.items())
The output will be:
[('name', 'John'), ('age', 30), ('city', 'New York')]
5. Dictionary Length
The length of a dictionary, i.e., the number of key-value pairs it contains, can be obtained using the len() function. Here's an example:
print(len(my_dict))
The output will be:
3
6. Conclusion
In this article, we have explored the basics of dictionaries in Python 3. We learned how to create a dictionary, access its values, modify its values, and use some of the handy methods provided. Dictionaries are incredibly useful for organizing and manipulating data in Python, and they should be part of every programmer's toolkit.