Adventures in Machine Learning

Mastering List of Dictionaries in Python: Creating Accessing and Updating Key-Value Pairs

Creating a List of Dictionaries in Python

1. Initializing a List

To create a list of dictionaries in Python, you first need to initialize an empty list using square brackets.

2. Creating Dictionaries

Next, you create multiple dictionaries with the necessary key-value pairs. Each dictionary represents a distinct set of data.

3. Appending Dictionaries to the List

Use the append() method to add each dictionary to the list.

ls_dict = []
ds1 = {'Name': 'John', 'Age': 25, 'Gender': 'Male'}
ds2 = {'Name': 'Jane', 'Age': 30, 'Gender': 'Female'}
ds3 = {'Name': 'Alex', 'Age': 35, 'Gender': 'Male'}
ls_dict.append(ds1)
ls_dict.append(ds2)
ls_dict.append(ds3)
print(ls_dict)
print(type(ls_dict))

This code snippet demonstrates creating a list of dictionaries, where each dictionary holds information about a person’s name, age, and gender.

Appending a Dictionary to the List of Dictionaries

Appending a new dictionary to an existing list is straightforward. Simply use the append() method again, providing the new dictionary as the argument.

ds4 = {'Name': 'LinuxforDevices', 'Age': 5, 'Gender': 'Male'}
ls_dict.append(ds4)

Now, ls_dict contains four dictionaries, including the newly added one.

Accessing Key:Value Pairs from the List of Dictionaries

To access key-value pairs, you can use indexing to target a specific dictionary within the list.

Let’s say you have a list of dictionaries containing information about books:

ls_dict = [{'Title': 'Python for Beginners', 'Author': 'John Doe'}, {'Title': 'Advanced Python Programming', 'Author': 'Jane Smith'}]

1. Accessing a Specific Dictionary

Use its index to retrieve a dictionary.

second_dict = ls_dict[1]

2. Accessing a Value

Use the dictionary’s key to get the corresponding value.

author = second_dict['Author']
print(author)

This will output “Jane Smith,” the author of the second book in the list.

Updating Key:Value Pairs in the List of Dictionaries

You can modify the key-value pairs within a dictionary in the list by adding new pairs, updating existing ones, or deleting pairs.

1. Adding a New Key:Value Pair

Use the update() method to add a new key-value pair to a dictionary.

ls_dict[0].update({'new_key': 'new_value'})
print(ls_dict[0])

This adds a new key “new_key” with a value of “new_value” to the first dictionary in the list.

2. Updating an Existing Key:Value Pair

Use indexing and the assignment operator to change the value of an existing key.

ls_dict[1]['Title'] = 'Mastering Python Programming'
print(ls_dict[1])

This updates the “Title” key in the second dictionary to “Mastering Python Programming.”

3. Deleting a Key:Value Pair

Use the del keyword to remove a specific key-value pair from a dictionary.

del ls_dict[0]['Title']
print(ls_dict[0])

This removes the “Title” key and its associated value from the first dictionary.

Conclusion

Creating and manipulating lists of dictionaries is a fundamental skill in Python, especially when working with complex datasets. This article demonstrated the basic operations of creating, appending, accessing, and updating key-value pairs within dictionaries within lists, empowering you to manage and analyze your data effectively.

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