matplotlib Annotation标注

import matplotlib.pyplot as pltimport numpy as npx = np.linspace(-3, 3, 50)y = 2*x + 1plt.figure(num=1, figsize=(8,5),)plt.plot(x, y,)ax = plt.gca()ax.spines['right'].set_color('none')ax.spines['top'].set_color('none')ax.xaxis.set_ticks_position('bottom')ax.spines['bottom'].set_position(('data', 0))ax.yaxis.set_ticks_position('left')ax.spines['left'].set_position(('data', 0))x0 = 1y0 = 2*x0 + 1plt.scatter(x0, y0, s=50, color='b')plt.plot([x0, x0], [y0,0], 'k--', lw=2.5)# method 1plt.annotate(    r'$2x+1=%s$' % y0,    xy=(x0, y0),    xycoords='data',    xytext=(+30, -30),    textcoords='offset points',    fontsize=16,    arrowprops=dict(arrowstyle='->',    connectionstyle='arc3, rad=.2'))# method 2plt.text(    -3.7,    3,    r'$This\ is\ the\ some\ text.\ \mu\ \sigma_i\ \alpha_t$',    fontdict={'size':16, 'color':'r'})plt.show()