Alpha: transparency

This example demonstrates using alpha for transparency.

import matplotlib.pyplot as plt

size = 256, 16
dpi = 72.0
figsize = size[0] / float(dpi), size[1] / float(dpi)
fig = plt.figure(figsize=figsize, dpi=dpi)
fig.patch.set_alpha(0)
plt.axes((0, 0.1, 1, 0.8), frameon=False)

for i in range(1, 11):
    plt.axvline(i, linewidth=1, color="blue", alpha=0.25 + 0.75 * i / 10.0)

plt.xlim(0, 11)
plt.xticks([])
plt.yticks([])
plt.show()