how to write a numpy array to a file in python
numpy.savetxt(fname, X, fmt='%.18e', delimiter=' ', newline='n',
header='', footer='', comments='# ', encoding=None)
x = y = z = np.arange(0.0,5.0,1.0)
np.savetxt('test.out', x, delimiter=',') # X is an array
np.savetxt('test.out', (x,y,z)) # x,y,z equal sized 1D arrays
np.savetxt('test.out', x, fmt='%1.4e') # use exponential notation