Bug summary

From matplotlib/ipympl#405 it seems that if you repreatedly run a cell with plt.figure(num=1) and then plot a new line you will only ever have a plot with one line on it.

Code for reproduction

Cell 1

%matplotlib nbagg
import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(-np.pi/2, np.pi/2)
i=0

Cell 2 (run this one repeatedly)

plt.figure(num=1)
plt.plot(x, np.sin(x*i))
i += 1

Actual outcome

Expected outcome

Do the equivalent from ipython:

import matplotlib.pyplot as plt
import numpy as np

plt.ion()
x = np.linspace(-np.pi/2, np.pi/2)

# each iteration of loop represents a cell re-execution
i = 0
def run_cell():
    global i
    plt.figure(num=1)
    plt.plot(x, np.sin(x*i))
    i += 1

Additional information

No response

Operating system

No response

Matplotlib Version

3.5.1

Matplotlib Backend

nbagg

Python version

3.9.7

Jupyter version

6.4.4

Installation

pip