Safe Nested Dictionary Traversaleasy

Safe Nested Dictionary Traversal

easy Python for AI 10–15 min

NumPy allowed · plain Python earns 10 bonus points

Implement defensive nested property lookup (optional chaining) -- essential for safely querying deeply nested REST payloads, GraphQL responses, and LLM structured outputs.

Related Skills

Language Fundamentals

Task

Implement safe_nested_get(data, keys, default=None): walk through keys sequentially within data. If at any stage a key does not exist or the current object is not a dictionary, return default. If keys is empty, return data.

Function Signature

safe_nested_get(data: dict, keys: list[str], default=None)

Examples

Example 1: Deeply Nested Key Found
Input: data = {'user': {'profile': {'name': 'Ada Lovelace'}}}
keys = ['user', 'profile', 'name']
default = 'Unknown'
Output: 'Ada Lovelace'

Example 2: Key Missing Along Path
Input: data = {'user': {'id': 42}}
keys = ['user', 'email']
default = 'no-email'
Output: 'no-email'

Constraints

Libraries are allowed; a plain-Python solution earns 10 bonus points.
Must never raise KeyError, TypeError, or IndexError during traversal.
Returns default whenever traversal cannot proceed.
Empty keys list returns data directly.

Python3Saved ✓

def safe_nested_get(data: dict, keys: list[str], default=None):

"""Safely traverse a nested dictionary path without KeyError or TypeError.

Walks down keys in order. If any key is missing or an intermediate

value is not a dict, returns default. If keys is empty, returns data."""

# Your implementation here

pass

Case 1: Deeply Nested Key Found

Input: data = {'user': {'profile': {'name': 'Ada Lovelace'}}}
keys = ['user', 'profile', 'name']
default = 'Unknown'

Expected: 'Ada Lovelace'

Case 2: Key Missing Along Path

Input: data = {'user': {'id': 42}}
keys = ['user', 'email']
default = 'no-email'

Expected: 'no-email'