Left Join
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
- Seniority
- L4
Interview Prompt
Given two lists of dicts (left, right) and a shared key name, left-join the lists the way SQL does: for each left record, find the first right record whose key matches and merge its non-key fields into the left record. If no right-side match exists, the row must still include every right-side column, filled with None (the SQL NULL). The set of right-side columns is the union of all keys appearing in the right list, minus the join key. Return the list of merged dicts in left order. An empty left list yields an empty list.
Summary
Keep the left side. Match what you can.
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