The scipy.signal module contains filter functions and B-spline interpolation algorithms.
Note
Spline interpolation uses a polynomial called a spline for interpolation (see http://en.wikipedia.org/wiki/Spline_interpolation). The interpolation then tries to glue splines together to fit the data. B-spline is a type of spline.
A SciPy signal is defined as an array of numbers. An example of a filter is the detrend() function. This function takes a signal and does a linear fit on it. This trend is then subtracted from the original input data.