设置坐标轴

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-3, 3, 50)
y1 = 2*x+1
y2 = x**2

plt.figure()
plt.plot(x, y2)
plt.plot(x, y1, color='red', linewidth=1,linestyle='--')

plt.xlim((-1, 2))
plt.ylim((-2,3))
plt.xlabel('I am x')
plt.ylabel('I am y')

new_ticks = np.linspace(-1, 2, 5)
print(new_ticks)
plt.xticks(new_ticks)
plt.yticks([-2,-1.8,-1,1,1.22,3], [r'$really\ bad$',r'$bad$',r'$normal$',r'$good$',r'$really\ good$'])

plt.show()