x = list(range(100))
y = list(range(100, 200))
fig = plt.figure()
ax1 = fig.add_subplot(111)
ax1.scatter(x[:4], y[:4], s=10, c='b', marker='s', label='first')
ax1.scatter(x[40:], y[40:], s=10, c='r', marker='o', label='second')
plt.legend(loc='upper left')
plt.show()
MatPlotLib: Multiple datasets on the same scatter plot