I’m trying to design a simple Butterworth bandpass filter in SciPy, and I’m running into some strange results. This is giving strange results, as can be seen from the image below (Butterworth filters from order 1-10). I thought the filter was supposed to become increasingly rectangular as the order increased? Does anyone know how to design a simple Butterworth filter in SciPy? Answer The frequency response of the Butterworth filter is not real-valued. When plotting the complex-valued response using plt.plot(), only the real component is shown. You should see a warning: To examine the filter’s gain, plot the magnitude of