fromthreadingimportThreadfromioimportBytesIOOBJ=BytesIO()deftest1():for_inrange(1000):setattr(OBJ,'x',1)OBJ.__dict__.pop('x',None)deftest2():for_inrange(1000):OBJ.getvalue() 
threads= []for_inrange(4):threads.append(Thread(target=test1))threads.append(Thread(target=test2))fortinthreads:t.start()fortinthreads:t.join()

WARNING: ThreadSanitizer: data race (pid=2885807)  Write of size 1 at 0x7fffb60c0108 by thread T1:    #0 new_keys_object /cpython/Objects/dictobject.c:795:22 (python3.15t+0x29cfbf)     #1 dictresize /cpython/Objects/dictobject.c:2078:15 (python3.15t+0x2a29bb)     #2 insertion_resize /cpython/Objects/dictobject.c:1770:12 (python3.15t+0x2a24bd)     #3 insert_combined_dict /cpython/Objects/dictobject.c:1787:13 (python3.15t+0x2a24bd)    #4 insertdict /cpython/Objects/dictobject.c:1909:13 (python3.15t+0x291d6d)     #5 setitem_take2_lock_held /cpython/Objects/dictobject.c:2674:12 (python3.15t+0x291217)     #6 setitem_lock_held /cpython/Objects/dictobject.c:2711:12 (python3.15t+0x29daf3)     #7 _PyDict_SetItem_LockHeld /cpython/Objects/dictobject.c:6840:16 (python3.15t+0x29daf3)    #8 _PyObjectDict_SetItem /cpython/Objects/dictobject.c:7539:11 (python3.15t+0x2a1907)     #9 _PyObject_GenericSetAttrWithDict /cpython/Objects/object.c:2006:19 (python3.15t+0x2c9664)     #10 PyObject_GenericSetAttr /cpython/Objects/object.c:2034:12 (python3.15t+0x2c9db7)     #11 PyObject_SetAttr /cpython/Objects/object.c:1479:15 (python3.15t+0x2c67df)     #12 builtin_setattr_impl /cpython/Python/bltinmodule.c:1744:9 (python3.15t+0x4199f7)     #13 builtin_setattr /cpython/Python/clinic/bltinmodule.c.h:692:20 (python3.15t+0x4199f7)    #14 _Py_BuiltinCallFast_StackRefSteal /cpython/Python/ceval.c:812:11 (python3.15t+0x41f994)     #15 _PyEval_EvalFrameDefault /cpython/Python/generated_cases.c.h:2322:35 (python3.15t+0x4267f4)     #16 _PyEval_EvalFrame /cpython/./Include/internal/pycore_ceval.h:118:16 (python3.15t+0x41e7a0)     #17 _PyEval_Vector /cpython/Python/ceval.c:2094:12 (python3.15t+0x41e7a0)    #18 _PyFunction_Vectorcall /cpython/Objects/call.c (python3.15t+0x20b19f)     #19 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x20f876)     #20 method_vectorcall /cpython/Objects/classobject.c:73:20 (python3.15t+0x20f876)    #21 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x471ed1)     #22 context_run /cpython/Python/context.c:727:29 (python3.15t+0x471ed1)    #23 method_vectorcall_FASTCALL_KEYWORDS /cpython/Objects/descrobject.c:421:24 (python3.15t+0x2243f7)     #24 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x20ab23)     #25 PyObject_Vectorcall /cpython/Objects/call.c:327:12 (python3.15t+0x20ab23)    #26 _Py_VectorCallInstrumentation_StackRefSteal /cpython/Python/ceval.c:762:11 (python3.15t+0x41f3cc)     #27 _PyEval_EvalFrameDefault /cpython/Python/generated_cases.c.h:1788:35 (python3.15t+0x425236)     #28 _PyEval_EvalFrame /cpython/./Include/internal/pycore_ceval.h:118:16 (python3.15t+0x41e7a0)     #29 _PyEval_Vector /cpython/Python/ceval.c:2094:12 (python3.15t+0x41e7a0)    #30 _PyFunction_Vectorcall /cpython/Objects/call.c (python3.15t+0x20b19f)     #31 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x20f876)     #32 method_vectorcall /cpython/Objects/classobject.c:73:20 (python3.15t+0x20f876)    #33 _PyVectorcall_Call /cpython/Objects/call.c:273:16 (python3.15t+0x20ae2b)     #34 _PyObject_Call /cpython/Objects/call.c:348:16 (python3.15t+0x20ae2b)    #35 PyObject_Call /cpython/Objects/call.c:373:12 (python3.15t+0x20ae95)     #36 thread_run /cpython/./Modules/_threadmodule.c:387:21 (python3.15t+0x5f03d2)     #37 pythread_wrapper /cpython/Python/thread_pthread.h:234:5 (python3.15t+0x521417)   Previous read of size 1 at 0x7fffb60c0108 by thread T2:    #0 do_lookup /cpython/Objects/dictobject.c:1002:19 (python3.15t+0x28e1fb)     #1 unicodekeys_lookup_unicode_threadsafe /cpython/Objects/dictobject.c:1445:12 (python3.15t+0x28e1fb)    #2 lookup_threadsafe_unicode /cpython/Objects/dictobject.c:1589:21 (python3.15t+0x28edc1)     #3 _PyDict_GetMethodStackRef /cpython/Objects/dictobject.c:1675:25 (python3.15t+0x28f031)     #4 _PyObject_GetMethodStackRef /cpython/Objects/object.c:1759:21 (python3.15t+0x2c8ecd)     #5 _PyEval_EvalFrameDefault /cpython/Python/generated_cases.c.h:7883:35 (python3.15t+0x4317eb)     #6 _PyEval_EvalFrame /cpython/./Include/internal/pycore_ceval.h:118:16 (python3.15t+0x41e7a0)     #7 _PyEval_Vector /cpython/Python/ceval.c:2094:12 (python3.15t+0x41e7a0)    #8 _PyFunction_Vectorcall /cpython/Objects/call.c (python3.15t+0x20b19f)     #9 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x20f876)     #10 method_vectorcall /cpython/Objects/classobject.c:73:20 (python3.15t+0x20f876)    #11 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x471ed1)     #12 context_run /cpython/Python/context.c:727:29 (python3.15t+0x471ed1)    #13 method_vectorcall_FASTCALL_KEYWORDS /cpython/Objects/descrobject.c:421:24 (python3.15t+0x2243f7)     #14 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x20ab23)     #15 PyObject_Vectorcall /cpython/Objects/call.c:327:12 (python3.15t+0x20ab23)    #16 _Py_VectorCallInstrumentation_StackRefSteal /cpython/Python/ceval.c:762:11 (python3.15t+0x41f3cc)     #17 _PyEval_EvalFrameDefault /cpython/Python/generated_cases.c.h:1788:35 (python3.15t+0x425236)     #18 _PyEval_EvalFrame /cpython/./Include/internal/pycore_ceval.h:118:16 (python3.15t+0x41e7a0)     #19 _PyEval_Vector /cpython/Python/ceval.c:2094:12 (python3.15t+0x41e7a0)    #20 _PyFunction_Vectorcall /cpython/Objects/call.c (python3.15t+0x20b19f)     #21 _PyObject_VectorcallTstate /cpython/./Include/internal/pycore_call.h:136:11 (python3.15t+0x20f876)     #22 method_vectorcall /cpython/Objects/classobject.c:73:20 (python3.15t+0x20f876)    #23 _PyVectorcall_Call /cpython/Objects/call.c:273:16 (python3.15t+0x20ae2b)     #24 _PyObject_Call /cpython/Objects/call.c:348:16 (python3.15t+0x20ae2b)    #25 PyObject_Call /cpython/Objects/call.c:373:12 (python3.15t+0x20ae95)     #26 thread_run /cpython/./Modules/_threadmodule.c:387:21 (python3.15t+0x5f03d2)     #27 pythread_wrapper /cpython/Python/thread_pthread.h:234:5 (python3.15t+0x521417)SUMMARY: ThreadSanitizer: data race /cpython/Objects/dictobject.c:795:22 in new_keys_object