Appending to list in Python dictionary

Python dictionaries are powerful data structures that allow you to store and retrieve data using key-value pairs. Appending an item to a list within a dictionary involves accessing the list by its corresponding key and then using the append() method to add the new item to the list.

Example

Input: {'Destination': 'China', 'Nationality': 'Italian', 'Age': [20]}
Output: {'Destination': 'China', 'Nationality': 'Italian', 'Age': [20, 'Twenty']}
Explaination: Appended "Twenty" in the list of keys of Age.

Appending to List in Python Dictionary

In Python, we can append to a dictionary in several ways:

• Using += Operator
• Using List append() Method
• Using List append() Method
• Using defaultdict() Method
• Using update() Function
• Appending Values to a List in Key

Using += Operator

In this method, we will use the += operator to append a Python list into the dictionary, for this we will take a dictionary and then add elements as a list into the dictionary.

Output:

Original: {'Destination': 'China', 'Nationality': 'Italian', 'Age': []}
Modified: {'Destination': 'China', 'Nationality': 'Italian', 'Age': [20, 'Twenty']}

Using List append() Method

In this method, we will use conditions for checking the key and then append to a dictionary list using the list append() method.

Output:

Original: {'Destination': 'China', 'Nationality': 'Italian', 'Age': [20]}
Modified: {'Destination': 'China', 'Nationality': 'Italian', 'Age': [20, 'Twenty']}

Using defaultdict() Method

In this method, we are using the defaultdict() function. It is a part of the collections module. We have to import the function from the collections module to use it in the program and then use it to append to a dictionary list. Since append takes only one parameter, to insert another parameter, repeat the append method.

Output:

Original: defaultdict(<class 'list'>, {})
Modified: defaultdict(<class 'list'>, {'Country': ['India', 'Pakistan']})

Using update() Function

We will use the Python dictionary update() function to add a new list to the dictionary. We can use the update() function to embed a dictionary inside another dictionary. 

Output:

Original: {'Destination': 'China', 'Nationality': 'Italian', 'Age': []}
Modified: {'Destination': 'China', 'Nationality': 'Italian', 'Age': [18, 20, 25, 29, 30]}

Appending Values to a List in Key

You can convert a list into a value for a key in a Python dictionary using dict() function. 

Output:

{'Age': [18, 20, 25, 29, 30]}