figure设置坐标轴

import matplotlib.pyplot as plt

import numpy as np

x=np.linspace(-3,3,50)

y1=x*2+1

y2=x**2

plt.plot(x,y1)

plt.figure(num=3,figsize=(8,5))

plt.plot(x,y2)

plt.plot(x,y1,color="red",linewidth=1.0,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,-1,1.22,3,],

        [r'$really\ bad$',r'$bad\ \alpha$',r'$normal$',r'$good$','$really\ good$'] 

#gca='get current axis'
  ax = plt.gca()
  ax.spines['right'].set_color('none')
  ax.spines['top'].set_color('none')
  ax.xaxis.set_ticks_position('bottom')
  ax.yaxis.set_ticks_position('left')
  ax.spines['bottom'].set_position(('data',0))
  ax.spines['left'].set_position(('data',0))

plt.show()