import numpy as np
import matplotlib.pyplot as plt

# 指数函数
# f(x) = a**x
x = np.linspace(-2, 2, 100)
y1 = (1 / 2) ** x
y2 = (1 / 4) ** x

plt.scatter(0, 1, marker='.', color='k')
plt.text(0.01, 1, r'(0,1)', fontsize=10)

plt.plot(x, y1, color='blue', linestyle='-')
plt.plot(x, y2, color='green', linestyle='-')

plt.axvline(0, color='gray', linestyle='--', alpha=0.8)
plt.axhline(0, color='gray', linestyle='--', alpha=0.8)
plt.axhline(1, color='red', linestyle='--', alpha=0.8)

plt.text(-2, 4, r'(1/2)^x', fontsize=15)
plt.text(-2, 16, r'(1/4)^x', fontsize=15)

plt.title('0<a<1')

plt.show()

输出结果：