Unique Elements From Objects | Dataford Interview Questions

LSEG Workspace may return repeated instrument records when results are combined from multiple market-data sources. Given a list of dictionary objects and the name of a field that uniquely identifies an object, return the unique objects in their original order, keeping only the first object for each identifier.

Formal Specification

Implement unique_objects(objects, key), where objects is a list of dictionaries and key is a string. Every dictionary contains the specified key, and its value is hashable. Return a new list containing the first dictionary encountered for each distinct key value. Do not modify the input list.

Objects with different values in non-key fields are still duplicates when their values for key match. The returned dictionaries should be the original objects, not copies.

Constraints

0 <= len(objects) <= 100,000
Each object contains the specified key
Each key value is hashable
The input list must not be modified
The first object for each identifier must be retained

Function Signature

def unique_objects(objects, key):

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