vscode python debug iterator count() code showing is not correct #130104

[opticaloptical]

Environment data

• debugpy version: XXX (run import debugpy; print(debugpy.__version__) if uncertain)
  1.4.1

• OS and version: XXX
  -win 10 20H2 19042.1110 Windows Feature Experience Pack 120.2212.3530.0

• Python version (& distribution if applicable, e.g. Anaconda): XXX
  conda 4.10.3
  Python 3.8.10 (default, May 19 2021, 13:12:57) [MSC v.1916 64 bit (AMD64)] :: Anaconda, Inc. on win32

• Using VS Code or Visual Studio:
  版本: 1.58.2 (user setup)
  提交: c3f126316369cd610563c75b1b1725e0679adfb3
  日期: 2021-07-14T22:10:15.214Z
  Electron: 12.0.13
  Chrome: 89.0.4389.128
  Node.js: 14.16.0
  V8: 8.9.255.25-electron.0
  OS: Windows_NT x64 10.0.19042

Actual behavior

code:

from itertools import count
my_vowels = ['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']
current_counter = count()
string = "This is just a sentence."
for i in string:
  if i in my_vowels:
    print(f"Current vowel: {i}")
    print(f"Number of vowels found so far: {next(current_counter)}")

info:
local variable show:
count(1), count(3),count(4).......

Expected behavior

from itertools import count

my_vowels = ['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']

current_counter = count()
string = "This is just a sentence."

for i in string:
  if i in my_vowels:
    print(f"Current vowel: {i}")
    print(f"Number of vowels found so far: {next(current_counter)}")

info:
local variable show:
current_counter :1,2,3,4,5

Steps to reproduce:

1. XXX
   

[int19h]

I suspect this has to do with having a Watch window expression that calls next() on the iterator - next() advances the iterator to the next element every time it's called, and if you put it into Watch, the debugger has to call it to get the value. In fact, we don't guarantee anything about how many times any given Watch expression will be evaluated, so anything with side effects shouldn't be used there.

[opticaloptical]

ok ，thanks