pyFBS is an open-source Python package for Frequency Based Substructuring. The package implements an object-oriented approach for dynamic substructuring. State-of-the-art methodologies in frequency based substructuring, such as virtual point transformation and system equivalent model mixing, are available within the pyFBS. Each method can be used as a standalone or interchangeably with others. Tools are provided to easily visualize components and configure the measurement setup. Also operational deflection shapes and mode shapes can be animated directly within the 3D display. Furthermore, basic and application examples are available, together with numerical and experimental datasets, to enable the user to get familiar with the work flow of the package. This paper showcases the use of the pyFBS on two example structures. Firstly, a simple beam-like structure is used to depict the use of the 3D display, FRF synthetization, virtual point transformation and system equivalent model mixing. Secondly, an automotive test-structure is used to show the use of the pyFBS on real-life complex structure, where the in-situ transfer path analysis is used to characterize blocked forces. The development of the pyFBS is an ongoing effort, as it is actively being used as a research tool. Additional features and new methods will be integrated within the pyFBS in the near future.