State Machine Patterns

Concepts covered: pyMergeIntervals

A state machine is a model where a system can be in exactly one of a finite number of states at any time. The system transitions between states based on events or conditions. State machines are powerful because they make complex behavior explicit and predictable. Unlike implicit state tracked through multiple boolean flags, a state machine makes the current state crystal clear. Many real-world systems are naturally state machines: an order goes from "placed" to "paid" to "shipped" to "delivered". A user session transitions from "logged out" to "logged in" to "timed out". A document moves from "draft" to "review" to "approved" to "published". Modeling these as explicit state machines makes the logic clear and bugs easier to find. States and Transitions A state machine has states (the possib

About This Interactive Section

This section is part of the Control Flow: Advanced lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live PostgreSQL database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

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