# Define compose(f, g) that returns a function applying f(g(x))

Canonical URL: <https://datadriven.io/problems/define-composef-g-that-returns-a-function-applying-fgx-f3b9233f>

Domain: Python · Difficulty: medium

## Problem

Define compose(f, g) that returns a function applying f(g(x)). Given double = lambda n: n * 2 and inc = lambda n: n + 1, build f = compose(double, inc). Print f(3) (should be 8 because (3+1)*2).

## Related

- [All practice problems](https://datadriven.io/problems)
- [Mock interview mode](https://datadriven.io/interview/define-composef-g-that-returns-a-function-applying-fgx-f3b9233f)
- [Python Interview Questions](https://datadriven.io/python-interview-questions)
- [Data Engineering Interview Prep Guide](https://datadriven.io/data-engineer-interview-prep)
- [Daily Challenge](https://datadriven.io/daily)

---

Source: DataDriven (https://datadriven.io). 100% free data engineering interview prep. Live code execution against Postgres 16, Python 3.11, and Spark sandboxes. No paywall, no premium tier, no signup gate.