[Python] How to draw dotted line in the graph with text written on it? [duplicate]

I have plotted a graph using matplotlib. I want to make straight lines with text written on it parallel to y axis in the graph at certain places.Does anyone know how to do that? look at the images for more clarity :



The image has the desired dotted lines that i want to plot. I want to draw lines just like in the image for the "leave decision", vertical lines parallel to y axis with leave decision written on it.

e.g code :

import matplotlib.pyplot as plt

r=[70,70,70,70]
e=[0,0,0,0]
r_0=[70]
r_1=[70]
r_2=[70]
r_3=[70]

for i in range(5):
r[0]=r[0]*0.9
r_0.append(r[0])
e[0]=e[0]+1



if r[1]<=200 :
r[1]=r[1]+4
r_1.append(r[1])


if r[2]<=200 :
r_2.append(r[2])
r[2]=r[2]+8


if r[3]<=200 :
r_3.append(r[3])
r[3]=r[3]+16


for i in range(5):
r[1]=r[1]*0.9
r_1.append(r[1])
e[1]=e[1]+1



if r[0]<=200 :
r[0]=r[0]+2
r_0.append(r[0])


if r[2]<=200 :
r[2]=r[2]+8
r_2.append(r[2])



if r[3]<=200 :
r[3]=r[3]+16
r_3.append(r[3])
else:
r_3.append(214)


for i in range(5):
r[2]=r[2]*0.9
r_2.append(r[2])
e[2]=e[2]+1



if r[0]<=200 :
r[0]=r[0]+2
r_0.append(r[0])


if r[1]<=200 :
r[1]=r[1]+4
r_1.append(r[1])


if r[3]<=200 :
r[3]=r[3]+16
r_3.append(r[3])

else:
r_3.append(214)


for i in range(5):
r[3]=r[3]*0.9
r_3.append(r[3])
e[3]=e[3]+1


if r[0]<=200 :
r[0]=r[0]+2
r_0.append(r[0])


if r[2]<=200 :
r[2]=r[2]+8
r_2.append(r[2])


if r[1]<=200 :
r[1]=r[1]+4
r_1.append(r[1])


x=range(21)
xb, r_0b = x[1:6], r_0[1:6]
plt.plot(x,r_0,'--')
plt.plot(xb, r_0b, 'tab:blue', marker='D')

x=range(21)
xb, r_1b = x[6:11], r_1[6:11]
plt.plot(x,r_1,'--')
plt.plot(xb, r_1b, 'tabrange', marker='D')

x=range(21)
xb, r_2b = x[11:16], r_2[11:16]
plt.plot(x,r_2,'--')
plt.plot(xb, r_2b, 'tab:green', marker='D')

x=range(21)
xb, r_3b = x[16:21], r_3[16:21]
plt.plot(x,r_3,'--')
plt.ylim(0,250)
plt.xlabel("Time")
plt.ylabel("Reward")
plt.title("Reward_Dynamics_B_3")
plt.plot(xb, r_3b, 'tab:red', marker='D')


My code output :

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