Dictionaries

Dictionaries in Python are an ordered collection of key-value pairs. They allow you to store multiple items in a single variable. Dictionary items are enclosed within curly brackets {} and separated by commas.

Creating a dictionary:

info = {'name': 'Ken', 'age': 19, 'eligible': True}
print(info)

Output:

{'name': 'Ken', 'age': 19, 'eligible': True}

Accessing single values using keys:

info = {'name': 'Ken', 'age': 19, 'eligible': True}
print(info['name'])
print(info.get('eligible'))

Output:

Ken
True

Accessing multiple values using values():

info = {'name': 'Ken', 'age': 19, 'eligible': True}
print(info.values())

Output:

dict_values(['Ken', 19, True])

Accessing keys using keys():

info = {'name': 'Ken', 'age': 19, 'eligible': True}
print(info.keys())

Output:

dict_keys(['name', 'age', 'eligible'])

Accessing key-value pairs using items():

info = {'name': 'Ken', 'age': 19, 'eligible': True}
print(info.items())

Output:

dict_items([('name', 'Ken'), ('age', 19), ('eligible', True)])

dict.fromkeys(): Creating a Dictionary with Default Values

keys = ['a', 'b', 'c']
default_value = 0
my_dict = dict.fromkeys(keys, default_value)
print(my_dict)

Output:

{'a': 0, 'b': 0, 'c': 0}

This method is particularly useful when you need to initialize a dictionary with a common default value for multiple keys.

Using the update() Method: The update() method allows you to merge the contents of another dictionary into the one created with fromkeys(). Here's how you can use it:

my_dict = dict.fromkeys(['a', 'b', 'c'], 0)
new_dict = {'b': 2, 'd': 4}
my_dict.update(new_dict)  # Update my_dict with key-value pairs from new_dict

After the update, my_dict will look like this:

{'a': 0, 'b': 2, 'c': 0, 'd': 4}

Conclusion

Python dictionaries are versatile data structures that store key-value pairs. They provide efficient access to values using keys. With curly brackets and commas, dictionaries are easy to create and manipulate. Accessing values, keys, or key-value pairs is straightforward using built-in methods like values(), keys(), and items(). Dictionaries empower you to efficiently organize and retrieve data, making them a valuable tool in Python programming.