Downstream

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

Domain

Python

Difficulty

hard

Seniority

L6

Problem

You're writing the executor at the core of a small pipeline orchestrator. `tasks` maps each task name to its `deps` (names of tasks that must run first) and `func`, the source text of a lambda that takes a dict of its dependencies' results, keyed by dependency name, and returns this task's output. Run each task once all of its prerequisites have run, return a dict from task name to result, and raise if no valid run order exists because the dependencies form a loop.

Summary

Nothing runs until what it needs has run.

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