Nested Dict Metrics Summary | Dataford Interview Questions

Write a Python function that parses a nested dictionary and outputs a dictionary summarizing metrics by user key.

Asked in the ETL 1 stage. The input may contain nested dictionaries and lists. Every dictionary with a user field represents a record; aggregate its other numeric fields into the result for that user. Ignore nonnumeric fields and the user field.

Contract

Implement summarize_by_user(data). Return a dictionary mapping each user value to a dictionary of summed metric values. Traverse all nested dictionaries and lists. Preserve metric names, and omit users with no numeric metrics.

Constraints

The structure contains at most 1,000 dictionaries and lists
Every record is a dictionary containing a hashable user value
Metric values are integers or floats
Non-numeric fields and the user field must be ignored
Users with no numeric metrics are omitted from the result

Function Signature

def summarize_by_user(data):

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