Evaluating expression of large objects from the debug console is extremely slow

I'm seeing an issue that apparently hasn't been reported yet. I have a fairly large dictionary in memory and when I want to get its length from the debug console it takes tens of seconds. Obviously, getting the repr of the dict takes that much time but I only want to get its length.

Code to reproduce:

from unittest import TestCase
from collections import defaultdict
import numpy as np
from types import SimpleNamespace

class MyTest(TestCase):
    def test_large_defaultdict(self):
        d = defaultdict(lambda: defaultdict(list))
        for k in 'abcdef':
            for l in 'ghijk':
                for i in range(10000):
                    d[k][l].append(SimpleNamespace(
                        key = k,
                        cycle = np.arange(20),
                        value = np.zeros(20)
                    ))

        pass

Set breakpoint on pass and try to evaluate len(d) from the debug console after the breakpoint is hit. This warning is printed in the console:

pydevd warning: Computing repr of d (defaultdict) was slow (took 42.36s)
Customize report timeout by setting the `PYDEVD_WARN_SLOW_RESOLVE_TIMEOUT` environment variable to a higher timeout (default is: 0.5s)

Yes, it is slow but why is repr called to print the number of items?

Commencez par la reproduction dans test.py et l’évaluation de len(d) dans la console de débogage, puis suivez le chemin de résolution de valeur du débogueur qui émet l’avertissement concernant repr lent. Comparez l’évaluation de len(d) à l’inspection directe de l’objet et identifiez où la représentation est calculée inutilement. Le travail est terminé lorsque l’évaluation de la longueur d’un objet volumineux n’entraîne plus le délai de repr et que le comportement est couvert par un test de régression.