from scipy import array, zeros, signal
from scipy.fftpack import fft, ifft, convolve
def conv(f, g):
  # transform f and g to frequency domain
  F = fft(f)
  G = fft(g)
  # multiply entry-wise
  C = F * G
  # transfer C to time domain
  c = ifft(C)

  return c

conv(f,g) = [ 34.+0.j  32.+0.j  34.+0.j  40.+0.j]
convolve.convolve(f,g) = [  1.48219694e-322   2.07507571e-322   3.06320700e-322   3.26083326e-322]
signal.convolve(f,g,'same') = [14 26 40 29]

def direct(f,g):
    r = zeros(len(f))
    for k in range(len(f)):
        for p in range(len(f)):
            r[k] = r[k] + (f[p] * g[k-p])
    return r

f = np.concatenate((f, np.zeros(4)))
g = np.concatenate((g, np.zeros(4)))