RNA interference (RNAi) is a biological mechanism for targeted inhibition of gene expression. It has also been used routinely to discover genes involved in the interaction of plants with pathogenic fungi. To minimize the miss-targeting of unrelated genes and to maximize the RNAi efficiency, we have developed a PyQt based cross- platform software tool called “si-Fi”. Our aim of the talk is to show that also hobby programmers can use Python in a very useful way.