Calculate Average Event Value by User ID

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Q: What difficulty level is this coding question?

This is a Medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Technical Screen rounds at Upstart.

Q: What role is this question designed for?

This question is commonly asked for Data Scientist candidates at Upstart during technical interviews.

Question

events

+----+---------+------------+-------+---------------------+
| id | user_id | event_type | value | timestamp           |
+----+---------+------------+-------+---------------------+
| 1  | 42      | click      | 3.5   | 2024-03-10 10:00:00 |
| 2  | 17      | view       | 1.0   | 2024-03-10 10:01:05 |
| 3  | 42      | purchase   | 7.0   | 2024-03-10 10:02:30 |
| 4  | 99      | click      | 2.3   | 2024-03-10 10:04:11 |
| 5  | 17      | purchase   | 4.7   | 2024-03-10 10:05:45 |
+----+---------+------------+-------+---------------------+

##### Scenario

You receive an API response that is a Python list of JSON objects, each describing a user event coming from a mobile-app funnel.

##### Question

Write Python code that, given a list like events = [{"id":1,"user_id":42,"event_type":"click","value":3.5,"timestamp":"2024-03-10 10:00:00"}, ...], produces a dictionary mapping each user_id to the average value of their events. Return the result sorted by descending average value.

##### Hints

Use defaultdict / pandas groupby; iterate only once if possible.

PracHub · Accepted Answer

This question evaluates a candidate's skill in group-wise aggregation and data transformation on JSON-like event streams, specifically computing per-user average metrics and producing ranked results.

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