Python怎么在柱形图上添加数字

在Python中，我们可以使用matplotlib库来创建柱状图，并在每个柱子上添加数字标签。下面是一个简单的例子：

import matplotlib.pyplot as plt
import numpy as np

# 数据
bar_width = 0.35
x = np.arange(4)
menMeans = (20, 35, 30, 35)  # 柱状图的数据
womenMeans = (25, 32, 34, 3.5)

# 创建图形
fig, ax = plt.subplots()

# 创建男性和女性的柱状图
rects1 = ax.bar(x - bar_width/2, menMeans, bar_width, label='Men')
rects2 = ax.bar(x + bar_width/2, womenMeans, bar_width, label='Women')

# 添加数值标签
for rect in rects1:
    height = rect.get_height()
    ax.annotate('{}'.format(height), xy=(rect.get_x() + rect.get_width() / 2, height),
                xytext=(0, 3),  # 3 points vertical offset
                textcoords="offset points",
                ha='center', va='bottom')  # 'bottom' for value below the bar

for rect in rects2:
    height = rect.get_height()
    ax.annotate('{}'.format(height), xy=(rect.get_x() + rect.get_width() / 2, height),
                xytext=(-3, 3),  # negative vertical offset
                textcoords="offset points",
                ha='center', va='bottom')

# 其他配置
ax.set_xlabel('Groups')
ax.set_ylabel('Scores')
ax.set_title('Scores by group and gender')
ax.set_xticks(x)
ax.set_xticklabels(('G1', 'G2', 'G3', 'G4'))
ax.legend()

plt.show()

在这个示例中，我们使用了`annotate`函数来在每个柱子上放置数字，`xy`参数表示文字的位置，`xytext`参数则确定文本离柱子底部的距离。