Python: Retrieve the value of the nested key indicated by the given selector list from a dictionary or list

Last update on June 28 2025 12:41:16 (UTC/GMT +8 hours)

71. Retrieve Nested Value by Selector List

Write a Python program to retrieve the value of the nested key indicated by the given selector list from a dictionary or list.

Sample Solution:

Python Code:

# Import the 'reduce' function from the 'functools' module and the 'getitem' function from the 'operator' module.
from functools import reduce
from operator import getitem

# Define a function 'test' that takes a dictionary 'd' and a list of 'selectors'.
def test(d, selectors):
    # Use 'reduce' to successively apply 'getitem' with each element in 'selectors' on the dictionary 'd'.
    # This effectively drills down into the dictionary using the sequence of selectors.
    return reduce(getitem, selectors, d)

# Create a nested dictionary 'users'.
users = {
    'Carla ': {
        'name': {
            'first': 'Carla ',
            'last': 'Russell'
        },
        'postIds': [1, 2, 3, 4, 5]
    }
}

# Call the 'test' function with two sets of selectors to access specific values within the 'users' dictionary.
# The first call accesses Carla's last name, and the second call accesses one of Carla's post IDs.
print(test(users, ['Carla ', 'name', 'last']))
print(test(users, ['Carla ', 'postIds', 1])) 

Sample Output:

Russell
2

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to access a nested value in a dictionary using a list of keys as the path.
• Write a Python program to implement a function that takes a nested dictionary and a selector list, returning the corresponding value.
• Write a Python program to traverse a nested dictionary or list using recursion and a selector list to retrieve a value.
• Write a Python program to use reduce() from functools to fetch a nested value based on a list of keys and indices.

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