from matplotlib import pyplot as plt
import pandas as pd

plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

df = pd.DataFrame({"col1": [1, 3, 5, 7, 1], "col2": [1, 5, 7, 9, 1]})
ax = df.plot(kind="bar")
ax2 = ax.twinx()

ax2.plot(ax.get_xticks(),
   df[['col1', 'col2']].values,
   linestyle='-',
   marker='o', linewidth=2.0)

plt.show()