Scientific software is in many disciplines crucial for understanding and reusing research data and a cornerstone for reproducibility of research results. The HeFDI Code School adresses the need of especially early career researchers on learning how to create good scientific software and increase the quality of their code for better reusability and sustainability. Together with the colleagues from Suresoft project and NFDI4Ing we offer a series of four workshops. Participants of these workshops will learn methods and techniques to increase the quality of their code, how to produce understandable and therefore reusable code, and to increase the sustainability of scientific software. Workshop - May 26 - Clean Code and Refactoring In the scientific environment with ever-changing requirements, it is important to produce source code that can be read, understood and modified by ourselves or others. This workshop will teach you how to apply clean code principles and refactoring techniques to produce high quality, maintainable code. Agenda: Motivation Clean Code and Refactoring with interactive hands-on examples Tipps for working with Python