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Lag Column
A medium Python mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- Python
- Difficulty
- medium
Interview Prompt
A window function step computes the previous value for each element in a time-series column. Return a list of the same length where each element is the value immediately before it in the input; the first element has no predecessor so it should be None.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Write your python solution with real code execution
- Get instant feedback and a hire/no-hire decision