def update(n, img):

    data = xt[n%niter,:,:]

    img.set_array(data.ravel())

    return img,

#xt是个三维数组

gridx = pl.arange(0., 402., 2.)

gridz = pl.arange(-400., 2., 2.)

x, z = pl.meshgrid(gridx, gridz)

base = xt[0,:,:]

fig2 = pl.figure()

img = pl.pcolormesh(x, z, base)

img.set_array(base.ravel())

im_ani = FuncAnimation(fig2, update,

        fargs=(img,),

        interval=400,

        blit=True)