Calculating and graphing a partial circle and inner circle in python

circle.py

import numpy as np
import matplotlib.pyplot as plt
from math import pi, cos, sin

arc_size = pi / 2
points = 20
inner_ratio = .4

theta = np.arange(0, arc_size, arc_size / points)

x1 = np.array([cos(t) for t in theta])
y1 = np.array([sin(t) for t in theta])

x2 = inner_ratio * x1
y2 = inner_ratio * y1

plt.plot(x1, y1, 'b.', label="Radius 1")
plt.plot(x2, y2, 'r.', label="Radius %.1f" % inner_ratio)

plt.title("Partial Circle")
plt.legend()
plt.show()