[Matplotlib-users] don't understand interactive mode

[Neal B. <ndb...@gm...>]

I am trying to update a figure in a loop:

    import matplotlib.pyplot as plt
    plt.ion()
    plt.figure (1)
    def c2r (z):
        return z.real, z.imag
    
    plt.hexbin (*c2r (run_ofdm (xconst_pred)[:opt.used]), mincnt=1)
    plt.draw()

But no figure appears on the screen.  What am I doing wrong?

This is using using Qt4Agg (I think, that's what's in my matplotlibrc)