The Listeners

A medium Python interview practice problem on DataDriven. Write and execute real python code with instant grading.

Domain

Python

Difficulty

medium

Seniority

L4

Problem

Implement an `EventEmitter` with `on(event, listener)` to subscribe, `emit(event, payload)` that returns the payload once per listener currently on that event, and `off(event, listener)` that drops the first matching listener. Then implement `event_broadcaster(op_names, op_args)`, which replays the parallel op sequence against one emitter and collects each result: `None` for the constructor, `on`, and `off`, and the payload list for `emit`.

Summary

Subscribers show up, listen, and sometimes leave.

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