Need to create and update figures in seperate cells?

还没有人认领这个 Issue。

Something I've seen in previous versions as well as the current version: In order to have a figure that dynamically updates while some code is executing (e.g. tracking the loss function of an optimization), I have to create the figure in a separate jupyter notebook cell and run it before a I run the code that updates. If I don't do this, then a blank figure shows and never updates. I'm using Jupyter lab. Wondering if I'm doing something wrong here? It would make the code cleaner and easier to run if it could all be put in a single cell.

Example:

Using the following function:
```python
def update_function(fig, ax):
while True:
# Do some computation
ax.clear() #clear previously drawn
ax.plot(some_data)
fig.canvas.draw() #force it to update
```

This works:

```python
# cell 1
fig, ax = plt.subplots()
```

```python
# cell 2
update_function(fig, ax)
```

But this does not:

```python
# one combined cell
fig, ax = plt.subplots()
update_function(fig, ax)
```

该 issue 未指定任何 repository 文件或测试。首先在 JupyterLab 中复现单独单元格和合并单元格的示例，然后比较长时间运行的 update_function 如何影响渲染。当合并单元格按要求更新图形，或 issue 记录了已确认的限制及其正确的 workaround 时，即可视为完成。

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