python - Set legend symbol opacity with matplotlib?

Question

I'm working on a plot with translucent 'x' markers (20% alpha). How do I make the marker appear at 100% opacity in the legend?

import matplotlib.pyplot as plt
plt.plot_date( x = xaxis, y = yaxis, marker = 'x', color=[1, 0, 0, .2], label='Data Series' )
plt.legend(loc=3, mode="expand", numpoints=1, scatterpoints=1 )

Answer 1

UPDATED: There is an easier way! First, assign your legend to a variable when you create it:

leg = plt.legend()

Then:

for lh in leg.legendHandles: 
    lh.set_alpha(1)

OR if the above doesn't work (you may be using an older version of matplotlib):

for lh in leg.legendHandles: 
    lh._legmarker.set_alpha(1)

to make your markers opaque for a plt.plot or a plt.scatter, respectively.

Note that using simply lh.set_alpha(1) on a plt.plot will make the lines in your legend opaque rather than the markers. You should be able to adapt these two possibilities for the other plot types.

Sources: Synthesized from some good advice by DrV about marker sizes. Update was inspired by useful comment from Owen.