import matplotlib.pylab as plt
marker_size=10
plt.figure()
plt.subplot(221)
plt.plot(
        range(10),
        linestyle='--',
        )
# drawing a line looks fine
plt.subplot(222)
plt.plot(
        range(10),
        marker='o',
        markersize=marker_size,
        markeredgewidth=2,
        markeredgecolor='r',
        )
# drawing markers is a bit problematic. There is always a line associated with markers.
plt.subplot(223)
plt.plot(
        range(10),
        linestyle=' ',
        marker='o',
        markersize=marker_size,
        markeredgewidth=2,
        markeredgecolor='r',
        )
# In order to ONLY draw markers, 'linestyle' should be set an empty string.
plt.subplot(224)
plt.plot(
        range(10),
        linestyle='--',
        linewidth=3,
        marker='o',
        markeredgewidth=2,
        markeredgecolor='r',
        markersize=marker_size,
        )
# It's even more strange that when you do want makers with a line, 'linestyle' also affects marker
# edges. In this example, line is set dashed. Then the marker's edges get dashed too!
plt.draw()
plt.show()