python画函数图像

import numpy as np
import matplotlib.pyplot as plt

import warnings
warnings.filterwarnings('ignore')
#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