How can I draw several lines in a matplotlib plot?

Question

I would also have a contour and vector field on the plot, and I would like to draw several lines on it. But when I used ax.plot for several times, only one line is shown.

like this

ax.plot([-1,-1], [1,1],linewidth=3,c='y')

Answer 1

import matplotlib.pyplot as plt

fig = plt.figure(figsize = (10,10))
ax = fig.add_subplot(111)
x1 = [10,20,30]
y1 = [20,40,10]
#plot the first line
ax.plot(x1, y1)

x2 = [10,20,30]
y2 = [40,10,30]
#plot the second line
ax.plot(x2, y2)

plt.show()

This piece of code should be able to produce multiple lines in the same axes