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The Gap Filler

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

Domain
Python
Difficulty
easy
Seniority
mid

Problem

Our time-series pipeline has gaps where sensors report None. Write a function called forward_fill that takes a list with None values and carries the most recent non-None value forward. If None appears before any real value, it stays None - the downstream model needs to know there's no history.

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