Hi, FYI I just merged two pull requests into Python 2.7, each add a new environment variable changing the behaviour in debug mode: bpo-31733: don't dump "[xxx refs]" into stderr by default anymore Set PYTHONSHOWREFCOUNT=1 commit 3c082a7fdb472f02bcac7a7f8fe1e3a34a11b70b bpo-31692, bpo-19527: don't dump allocations counts by default anymore Set PYTHONSHOWALLOCCOUNT=1 commit 7b4ba62e388474e811268322b47f80d464933541 I never ever used "[xxx refs]" to detect a reference leak. I only use "./python -m test -R 3:3 test_xxx" to detect reference leaks. To be honest, usually I only run such test explicitly when one of our "Refleaks" buildbot starts to comlain :-) Victor