如何在matplotlib中为来自dataframe的多组添加错误条？

import matplotlib.pyplot as plt
import pandas as pd

# 创建一个示例dataframe
data = {'Group 1': [10, 12, 15, 8],
        'Group 2': [13, 9, 11, 14],
        'Group 3': [7, 10, 9, 12]}
df = pd.DataFrame(data)

# 计算每组数据的均值和标准差
means = df.mean()
stds = df.std()

# 绘制柱状图
plt.bar(range(len(means)), means, yerr=stds, align='center', alpha=0.5)

# 设置x轴标签和标题
plt.xticks(range(len(means)), df.columns)
plt.xlabel('Groups')
plt.ylabel('Values')
plt.title('Error Bar Example')

# 显示图形
plt.show()