(a) The Archimedean spiral:
import numpy as np
import matplotlib.pyplot as plt
theta = np.linspace(0., 8*np.pi, 1000)
a, b = 0, 2.
plt.polar(theta, a+b*theta)
plt.show()
(b) The logarithmic spiral
import numpy as np
import matplotlib.pyplot as plt
theta = np.linspace(0, 8*np.pi, 1000)
a1 = 0.8
plt.polar(theta, a1**theta)
plt.show()