import matplotlib.pyplot as plt

import numpy as np

x = np.linspace(-1,1,50)

y1=x**2

y2=2*x+1

#第一个绘图框

plt.figure()

plt.plot(x,y1)

#第二个绘图框

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

plt.plot(x,y2)

plt.plot(x,y1,color="red",linewidth=1.0,linestyle="--")

plt.show()

import matplotlib.pyplot as plt

import numpy as np

x = np.linspace(-1,1,50)

y1=x**2

y2=2*x+1

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

plt.plot(x,y2)

plt.plot(x,y1,color="red",linewidth=1.0,linestyle="--")

#控制xy轴的数值范围

plt.xlim(-1,2)

plt.ylim(-3,3)

#x,y轴的标签

plt.xlabel("i am x")

plt.ylabel("i am y")

#更改x轴的数字标签

new_ticks=np.linspace(-1,2,5)

plt.xticks(new_ticks)

#更改y轴的数字标签（r是转义字符）

plt.yticks([-2,-1.8,-1,-1.22,-3,],

            [r"$really\ good\ \alpha$","normal","good","very good","nice"])

plt.show()