制作双色3D柱状图遇TypeError报错，求排查思路

问题场景 #

尝试制作沿纵轴分双色的3D柱状图，编写Python代码如下：

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

# 创建示例数据
x = np.array([1, 2, 3])
y = np.array([4, 5, 6])
z1 = np.array([1, 2, 3])
z2 = np.array([4, 5, 6])
z3 = np.array([7, 8, 9])
color1 = np.array(['r', 'g', 'b'])
color2 = np.array(['y', 'm', 'c'])

# 创建画布和3D轴
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

# 绘制第一组柱子
for i in range(len(x)):
    ax.bar(x[i], z1[i], y[i], zdir='y', color=color1[i], alpha=0.8)
    ax.bar(x[i], z1[i] - z1[i], y[i], zdir='y', color=color2[i], alpha=0.8)

# 绘制第二组柱子
for i in range(len(x)):
    ax.bar(x[i], z2[i], y[i]+0.5, zdir='y', color=color1[i], alpha=0.8)
    ax.bar(x[i], z2[i] - z2[i], y[i]+0.5, zdir='y', color=color2[i], alpha=0.8)

# 绘制第三组柱子
for i in range(len(x)):
    ax.bar(x[i], z3[i], y[i]+1.0, zdir='y', color=color1[i], alpha=0.8)
    ax.bar(x[i], z3[i] - z3[i], y[i]+1.0, zdir='y', color=color2[i], alpha=0.8)

# 设置轴标签和标题
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
ax.set_zlabel('Z axis')
ax.set_title('3D Bar Chart')

# 显示图像
plt.show()

在Windows 11系统的VSCode（Python 3.10）中运行时，出现如下报错：

Traceback (most recent call last):
File "c:\Users\16168\Documents\delta-scan-master\delta-scan-master\test\eval_test_display.py", line 73, in 
ax.bar(x[i], z1[i], y[i], zdir='y', color=color1[i], alpha=0.8)
File "C:\Users\16168\Documents\delta-scan-master\delta-scan-master\env\lib\site-packages\matplotlib\__init__.py", line 1459, in inner
return func(ax, *map(sanitize_sequence, args), **kwargs)
File "C:\Users\16168\Documents\delta-scan-master\delta-scan-master\env\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py", line 2318, in bar
zs = np.broadcast_to(zs, len(left))
TypeError: object of type 'numpy.int32' has no len()

报错原因解析 #

1. 报错行指向逻辑：报错回溯指向第73行的ax.bar调用，是因为错误是在调用该函数后，由matplotlib内部代码触发的。内部代码中的len(left)里的left是你传入的x[i]——单个numpy.int32标量，对单个整数调用len()自然会报错，而非你的代码里直接写了len()导致的问题。
2. 参数类型要求：mpl_toolkits.mplot3d.Axes3D.bar函数期望接收**序列类型（数组/列表）**作为位置参数，而非单个标量。当你传入单个标量时，函数内部无法对其执行len()操作，从而抛出类型错误。该问题和i的类型、len(x)的返回值无关。

解决思路与修正代码 #

方案1：将单个标量转为单元素数组 #

在循环中把每个传入的标量参数用np.array()包裹，转为单元素数组，满足函数对参数类型的要求：

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

# 创建示例数据
x = np.array([1, 2, 3])
y = np.array([4, 5, 6])
z1 = np.array([1, 2, 3])
z2 = np.array([4, 5, 6])
z3 = np.array([7, 8, 9])
color1 = np.array(['r', 'g', 'b'])
color2 = np.array(['y', 'm', 'c'])

# 创建画布和3D轴
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

# 绘制第一组柱子
for i in range(len(x)):
    ax.bar(np.array([x[i]]), z1[i], np.array([y[i]]), zdir='y', color=color1[i], alpha=0.8)
    ax.bar(np.array([x[i]]), 0, np.array([y[i]]), zdir='y', color=color2[i], alpha=0.8)

# 绘制第二组柱子
for i in range(len(x)):
    ax.bar(np.array([x[i]]), z2[i], np.array([y[i]+0.5]), zdir='y', color=color1[i], alpha=0.8)
    ax.bar(np.array([x[i]]), 0, np.array([y[i]+0.5]), zdir='y', color=color2[i], alpha=0.8)

# 绘制第三组柱子
for i in range(len(x)):
    ax.bar(np.array([x[i]]), z3[i], np.array([y[i]+1.0]), zdir='y', color=color1[i], alpha=0.8)
    ax.bar(np.array([x[i]]), 0, np.array([y[i]+1.0]), zdir='y', color=color2[i], alpha=0.8)

# 设置轴标签和标题
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
ax.set_zlabel('Z axis')
ax.set_title('3D Bar Chart')

# 显示图像
plt.show()

方案2：批量传入数组，避免循环（更高效） #

直接利用numpy数组的广播特性，一次性传入整组数据，无需循环，同时修正原代码中高度为0的无效柱子逻辑：

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

# 创建示例数据
x = np.array([1, 2, 3])
y = np.array([4, 5, 6])
z1 = np.array([1, 2, 3])
z2 = np.array([4, 5, 6])
z3 = np.array([7, 8, 9])
color1 = np.array(['r', 'g', 'b'])
color2 = np.array(['y', 'm', 'c'])
# 定义柱子下半段高度（可根据需求调整）
z_base = np.array([0.5, 1, 1.5])

# 创建画布和3D轴
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

# 第一组双色柱子：下半段+上半段
ax.bar(x, z_base, y, zdir='y', color=color2, alpha=0.8)
ax.bar(x, z1 - z_base, y, zdir='y', bottom=z_base, color=color1, alpha=0.8)

# 第二组双色柱子
ax.bar(x, z_base, y+0.5, zdir='y', color=color2, alpha=0.8)
ax.bar(x, z2 - z_base, y+0.5, zdir='y', bottom=z_base, color=color1, alpha=0.8)

# 第三组双色柱子
ax.bar(x, z_base, y+1.0, zdir='y', color=color2, alpha=0.8)
ax.bar(x, z3 - z_base, y+1.0, zdir='y', bottom=z_base, color=color1, alpha=0.8)

# 设置轴标签和标题
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
ax.set_zlabel('Z axis')
ax.set_title('3D Bar Chart')

# 显示图像
plt.show()

内容的提问来源于stack exchange，提问作者Koerner Gray Buchta