pyplot change property of text bxo code example

Example 1: plt text matplotlib white background

import numpy as np
import matplotlib.pyplot as plt
plt.figure()
ax = plt.subplot(111)
plt.plot(np.linspace(1,0,1000))
t = plt.text(0.03,.95,'text',transform=ax.transAxes,backgroundcolor='0.75',alpha=.5)
plt.show()

Example 2: plt text verticalalignment

plt.text(x, y, s, va = "center", ha = "center")