Python is one of the most extended programming languages nowadays, especially in molecular bioinformatics. One of the outcomes has been the creation of general purpose bioinformatics libraries, like Biopython. Nonetheless, they do not provide solution to every aspect of each research field included in the broad meaning of the word “bioinformatics”. This led us to the development of MEvoLib, the first molecular evolution library implemented in Python. It has been designed to provide support for some of the most well-known and used software tools in the field altogether with innovative methods to deal with specific problems when working with molecular sequences and phylogenetic trees. The aim of this talk is to go through MEvoLib’s design and the key parts of its implementation. For instance, it will show the main aspects of the design of the interface of modules that deal with external software tools and how they provide support for users with different level of expertise.