Industry 4.0 is driving a paradigm shift in manufacturing, aerospace and other sectors. Digital Twins (DTs) are a cornerstone of this transformation, offering real-time insights through data-driven simulations of physical systems. While standards like Functional Mock-up Interface (FMI) facilitate interoperability, there remains a lack of flexible, research-oriented tools that support rapid prototyping and seamless integration of AI (Artificial Intelligence) components into DTs. To address this gap, we introduce CoFMPy, an open-source platform-independent solution in Python that supports FMI standards for seamless co-simulation and rapid development of Proof of Concept DT applications. CoFMPy integrates a coordinator for efficient model orchestration and co-simulation, a communication module, and data storage capabilities for long-term data management and analysis. We briefly illustrate CoFMPy’s application through a case study from the European Project HECATE, which involves an AI-powered DT for efficient battery health monitoring in a hybrid aircraft. Source code, documentation and demos are available at https://github.com/IRT-Saint-Exupery/CoFMPy.