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?

从 test.py 中的复现和调试控制台对 len(d) 的求值开始，然后跟踪调试器发出慢速 repr 警告的值解析路径。将 len(d) 的求值与直接检查对象进行比较，并确定在哪个位置不必要地计算了表示形式。完成标准是：大型对象的长度求值不再产生 repr 延迟，并且该行为由回归测试覆盖。