Visualise My Python

A small Python execution visualizer built with:

• FastAPI backend
• Docker sandbox runner for executing user code
• Next.js frontend with editor, stepper, call stack, and heap views

Demo

Features

• Run Python code and trace execution step-by-step
• View current line in source
• Inspect call stack and function frames
• Inspect heap objects with reference-based serialization (Python Tutor-style)
• Sandboxed execution in Docker with basic hardening (--network none, memory/CPU limits, read-only FS, PID limits)

Project Structure

• backend/main.py - FastAPI API (POST /trace)
• backend/sandbox/runner.py - Python tracer + serializer executed inside Docker
• backend/sandbox/Dockerfile - sandbox image
• frontend/ - Next.js app (editor + visualizer UI)

Run Locally

1) Build the sandbox image

docker build -t python-visualizer-runner backend/sandbox

2) Start the backend

uvicorn backend.main:app --reload --host 127.0.0.1 --port 8000

3) Start the frontend

cd frontend
npm install
npm run dev

Open http://localhost:3000

Notes

• This is a side project and intended for local use.
• User code is executed with exec() inside a Docker container (not directly in the FastAPI process).
• If you expose the backend publicly, add stronger production hardening and authentication/rate limits.