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

Last update on April 19 2025 13:01:08 (UTC/GMT +8 hours)

Retrieve Nested Key Value

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

Use functools.reduce() to iterate over the selectors list.
Apply operator.getitem() for each key in selectors, retrieving the value to be used as the iteratee for the next iteration.

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 called 'get' that takes a dictionary 'd' and a list of 'selectors'.
def get(d, selectors):
  # Use the 'reduce' function to access nested dictionary values by applying 'getitem' successively.
  return reduce(getitem, selectors, d) 

# Create a nested dictionary 'users' with user information.
users = {
  'freddy': {
    'name': {
      'first': 'Fateh',
      'last': 'Harwood' 
    },
    'postIds': [1, 2, 3]
  }
}

# Example: Access values in the 'users' dictionary using nested selectors.
print(get(users, ['freddy', 'name', 'last']))
print(get(users, ['freddy', 'postIds', 1]))

Sample Output:

Harwood
2

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to retrieve a nested key value from a deeply nested dictionary using a list of keys, handling missing keys gracefully.
Write a Python program to extract a nested value from a dictionary where the key path is provided as a dot-separated string.
Write a Python program to retrieve nested key values from a list of dictionaries given a common selector list.
Write a Python program to extract nested values from a mixed dictionary and list structure using recursion.

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