Junior Data scientist

The Circularity team is looking for a Data Science/Engineering intern based in Lille.

At Decathlon, we are over 100,000 sports enthusiasts united by one mission: making sport and wellbeing accessible to all. What sets us apart is our integrated model: from R&D to logistics, we manage everything in-house to positively impact the lives of a billion people.

CONTEXT

The Circularity Domain In line with the Paris Agreement, Decathlon is making circularity the new norm. We are building a future where recycling, repairing, renting, and buying second-hand is as natural as buying new. We are decarbonizing our model to protect our shared playground.

The Planet Analytics/AI Team (PLANT) At the heart of the Circularity Domain, our team creates the intelligence that drives Decathlon's sustainable transformation. We turn raw data into concrete actions (dashboards, predictive and prescriptive Machine Learning models) to improve the business and protect the planet.

The AiGenda Project Our workshop technicians work in a dynamic and complex environment. Between diagnosing a bike, managing spare parts, and welcoming customers, they face constant dilemmas: how to minimize wait times while managing limited capacity? How to prioritize emergencies without breaking overall efficiency? AiGenda aims to automate these complex scheduling tasks. The goal: recommend the best return dates, manage inventory, and prioritize tasks so technicians can focus on their core craft: high-quality repair.

YOUR MISSION

Every optimization begins with creating a model faithful to reality. Your goal will be to contribute to the AiGenda project by building a "digital twin" of Decathlon's workshops, capable of adapting to a wide variety of situations.

Your Main Challenges

• Modeling: Use Markov Decision Processes (MDP) for complex decision problems and Discrete-Event Simulation (DES) for concurrent events.
• Development: Improve the current prototype based on SimPy + Gymnasium.
• Robustness & Visualization: Integrate visualizations (via Simbala) and strengthen the current implementation to make it more robust.
• Reality Check: Validate the model against field reality and define the right performance metrics.
• Optimization: Work on "Generalized Assignment Problem" type challenges.

YOUR PROFILE

If you love solving algorithmic puzzles and see code as a playground, you've come to the right place.

This Internship Is For You If

• From Theory to Practice: You have a strong grasp of abstract mathematical concepts and know how to transform them into elegant, high-performance Python code.
• Software Craftsmanship: For you, code that just "works" isn't enough. You apply SOLID principles and are committed to writing clean, tested, and maintainable code.
• Analytical Mindset: Debugging and profiling your code is second nature to you, allowing you to iterate quickly and effectively.
• Visual Storytelling: You know how to design clear visualizations and animations to make complex models understandable to everyone.
• Soft Skills: You are creative, humble, and not afraid to question your assumptions to keep progressing.

Your Background

• Master 1 or 2 student (Computer Science, Operations Research, or Applied Mathematics).

Our Technical Environment

• Python Master: Data structures, OOP (classes), Simpy, and visualization (Plotly / Matplotlib).
• Testing & Quality: Pytest, Unittest, and ideally the Hypothesis library.
• Versioning: Git is your daily tool.
• The "Little Extra": Basic knowledge in Tableau for dashboarding.

WHY JOIN US?

• Sport & Community: You will work in a vibrant workplace that encourages sports practice and team-building moments with your fellow teammates.
• Brand Ambassador: You will have the chance to test new Decathlon products and share your passion on the field by joining our internal sports clubs.
• Join a supportive community of interns and apprentice students: collaboration, conviviality, and dedicated events.
• Learning Culture: You are joining a Happy Trainees 2025 certified company, recognized for providing a high-quality learning environment for interns.
• Work Tools: Choice of hardware (Mac or Windows) provided in line with your missions and our social responsibility commitments.
• Commuting: 50% reimbursement of your public transportation pass.

DECATHLON DIGITAL CONTEXT
What if technology allowed us to push the boundaries and take sports experiences to new levels? That's exactly our goal at Decathlon Digital We are a team of 5,000+ experts in software engineering, product management, data, cloud, and cybersecurity, distributed across Paris, Lille, and Amsterdam. Together, we are creating the largest digital sports platform, leveraging tech innovation from design to value chain optimization, connected experiences and product second life.

Changing the game for good
. We are in this for the love of sports. And like everything we love, we want it to last. That's why we are embarking on a journey to create a more sustainable tech model, reducing our direct environmental impact while maintaining a safe, diverse, and inclusive space for all our people to learn and thrive together. Team up with us to design the digital future of sports.