Signals in the real world often have a periodic nature. A commonly used tool to deal with these signals is the Fourier transform. The Fourier transform is a transformation from the time domain into the frequency domain, that is, the linear decomposition of a periodic signal into sine and cosine functions with various frequencies.

The functions for Fourier transforms can be found in the scipy.fftpack module (NumPy also has its own Fourier package, numpy.fft). Included in the package are fast Fourier transforms, differential and pseudo-differential operators, as well as several helper functions. MATLAB users will be pleased to know that a number of functions in the scipy.fftpack module have the same names as their MATLAB counterparts and similar functions as their MATLAB equivalents.