Using pandas to plot barplots with error bars

What is your data shape?

For an n-by-1 data vector, you need a n-by-2 error vector (positive error and negative error):

import pandas as pd 
import matplotlib.pyplot as plt

df2 = pd.DataFrame([0.4, 1.9])
df2.plot(kind='bar', yerr=[[0.1, 3.0], [3.0, 0.1]])

plt.show()