A trend line sample in matplotlib Python

trendline_matplotlib.py

# draw the closing price and related trendlines (uptrend and downtrend)
fig, ax1 = plt.subplots(figsize=(15,10))

color = 'tab:green'
xdate = [x.date() for x in df.index]
ax1.set_xlabel('Date', color=color)
ax1.plot(xdate, df.Close, label="close", color=color)
ax1.tick_params(axis='x', labelcolor=color)
ax1.legend()

ax2 = ax1.twiny() # ax2 and ax1 will have common y axis and different x axis, twiny
ax2.plot(df.Number, df.Uptrend, label="uptrend")
ax2.plot(df.Number, df.Downtrend, label="downtrend")

plt.legend()
plt.grid()
plt.show()