如何创建带类别的Matplotlib条形图？

import matplotlib.pyplot as plt
import numpy as np

categories = ['类别1', '类别2', '类别3', '类别4']
values = [10, 15, 7, 12]

fig, ax = plt.subplots()
ax.bar(categories, values)

ax.set_title('带类别的条形图')
ax.set_xlabel('类别')
ax.set_ylabel('值')

plt.show()