The Fallback Layer

A easy Python interview practice problem on DataDriven. Write and execute real python code with instant grading.

Domain

Python

Difficulty

easy

Seniority

L3

Problem

A service builds its runtime config by layering environment values over a baseline. Start from `primary`, the values read from the environment, and keep every key it has; whenever one of those values is `None`, fall back to the same key in `defaults`. A key that lives only in `defaults` never makes it into the result, and a `None` with no matching default stays `None`.

Summary

When the live values come back empty, something has to stand in.

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