用python画图，y=x和y=x*x叠加在一起。并且标记x=1的点

# -*- coding: UTF-8 -*-

import matplotlib  as mpl
import numpy  as np
import matplotlib.pyplot as plt


import matplotlib  as mpl

import matplotlib.pyplot as plt




x=np.linspace(-5,5,100)
y1=x**2
y2=x



plt.figure()
plt.plot(x,y1,label='circle')
plt.plot(x,y2,color='red',linewidth=1.0,linestyle='--',label='line')

plt.legend(loc = 'best')

plt.xlim(-5,5)
plt.ylim(-5,5)
plt.xlabel('x')
plt.ylabel('y')


plt.yticks([-2,0,2],
           [r'$bad$',r'$normal$',r'$good$'])



#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))




x0=1.0
y0=x0
plt.scatter(x0,y0,s=50,color='red')
plt.plot([x0,y0],[y0,0],'k--')

plt.annotate(r'$x=y$',xy=(x0,y0),xycoords='data',xytext=(+3,1),arrowprops=dict(arrowstyle='->',connectionstyle='arc3,rad=0.2'))
#对线条做描述

plt.text(x0+3,y0+1,r'love')



plt.show()