import matplotlib.pyplot as plt
import numpy as np

rng = np.random.RandomState(0)
x = rng.randn(100)
y = rng.randn(100)
colors = rng.rand(100)
sizes = 1000 * rng.rand(100)

plt.scatter(x, y, c=colors, s=sizes, alpha=0.5, cmap="viridis")
plt.colorbar()  # show color scale

plt.show()