Windows10下Jupyter Lab提示Javascript Error: IPython is not defined问题求助

问题重现 #

将Jupyter Notebook创建的含Matplotlib动画的文件放到Windows10的Jupyter Lab中运行时，触发以下错误：

Javascript Error: IPython is not defined

同时伴随Matplotlib的警告：

C:\Users\marc_arias\AppData\Local\Programs\Python\Python311\Lib\site-packages\matplotlib\animation.py:879: UserWarning: Animation was deleted without rendering anything. This is most likely not intended. To prevent deletion, assign the Animation to a variable, e.g. `anim`, that exists until you output the Animation using `plt.show()` or `anim.save()`.
  warnings.warn(

运行的代码如下：

%matplotlib notebook

import itertools
import matplotlib.pyplot as plt
import numpy as np
import matplotlib.animation as animation

def data_gen():
    for cnt in itertools.count():
        t = cnt / 10
        yield t, np.sin(2*np.pi*t) * np.exp(-t/10.)

def init():
    ax.set_ylim(-1.1, 1.1)
    ax.set_xlim(0, 1)
    del xdata[:]
    del ydata[:]
    line.set_data(xdata, ydata)
    return line,

fig, ax = plt.subplots()
line, = ax.plot([], [], lw=2)
ax.grid()
xdata, ydata = [], []

def run(data):
    t, y = data
    xdata.append(t)
    ydata.append(y)
    xmin, xmax = ax.get_xlim()

    if t >= xmax:
        ax.set_xlim(xmin, 2*xmax)
        ax.figure.canvas.draw()
    line.set_data(xdata, ydata)

    return line,

ani = animation.FuncAnimation(fig, run, data_gen, interval=100, init_func=init,
                              save_count=100)
plt.show()

原因分析 #

• %matplotlib notebook是为传统Jupyter Notebook设计的交互式后端，依赖旧版IPython暴露的全局JavaScript对象IPython。
• Jupyter Lab的前端架构完全重构，不再提供这个全局IPython对象，导致渲染动画时触发JS错误。
• 动画被删除的警告是前端渲染失败的连锁反应：因为JS错误导致动画无法输出，Python端的动画对象被垃圾回收。

解决方案 #

1. 替换Matplotlib后端
   把代码开头的%matplotlib notebook替换为Jupyter Lab兼容的交互式后端：

   %matplotlib widget
   

   这个后端是matplotlib官方推荐的Jupyter Lab交互式渲染方案，支持动画、交互操作，不依赖旧版IPython JS API。

2. 安装必要依赖（如果widget后端不可用）
   如果运行%matplotlib widget提示错误，需要先安装ipympl包：

   pip install ipympl
   

   安装完成后重启Jupyter Lab，再运行代码即可正常渲染动画。

内容的提问来源于stack exchange，提问作者marc arias