## Problem A hardware camera has the following states: IDLE, INITIALIZING, PREVIEWING, CAPTURING, ERROR. Implement a state machine that enforces valid transitions and raises descriptive errors on invalid ones. ```python from enum import Enum, auto class CameraState(Enum): IDLE = auto() INITIALIZING = auto() PREVIEWING = auto() CAPTURING = auto() ERROR = auto() class Camera: def initialize(self) -> None: ... def start_preview(self) -> None: ... def capture(self) -> bytes: ... def stop(self) -> None: ... def reset(self) -> None: ... @property def state(self) -> CameraState: ... ``` **Valid transitions:** ``` IDLE -> INITIALIZING -> PREVIEWING -> CAPTURING -> PREVIEWING Any state -> ERROR -> IDLE (via reset) ``` ## Follow-ups 1. How would you represent the transition table as data (dict of dicts) rather than nested if-statements? 2. How do you ensure thread safety when two threads call `capture` and `stop` simultaneously? 3. How would you log every state transition for post-mortem debugging of a camera crash? 4. How would you test the ERROR -> IDLE recovery path in a unit test without real hardware?

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Camera States: Model a Camera State Machine with Valid Transitions and Error Handling

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Problem A hardware camera has the following states: IDLE, INITIALIZING, PREVIEWING, CAPTURING, ERROR. Implement a state machine that enforces valid transitions and raises descriptive errors on invalid ones. Valid transitions: Follow-ups How would you represent the transition table as data (dict of dicts) rather than nested if-statements? How do you ensure thread safety when two threads call capture and stop simultaneously? How would you log every state transition for post-mortem debugging of a c…

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This is a candidate experience report from a verkada interview during the phone round.

It covers the following topics: Coding, Phone .

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Camera States: Model a Camera State Machine with Valid Transitions and Error Handling

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