The following program can work well in Python 2. However it crashes in Python 3( 3.6-3.10 ) with the following error messages.
Program:
============================================
import sys,time, threading

class test:
    def test(self):
        pass


class test1:
    def run(self):
        for i in range(0,10000000):
            connection = test()
            sys.stderr.write(' =_= ')


def testrun():
    client = test1()
    thread = threading.Thread(target=client.run, args=())
    thread.setDaemon(True)
    thread.start()

    time.sleep(0.1)

testrun()
============================================

Error message:
------------------------------------------------------------------------------

=_=  =_=  =_=  =_=  =_=  ......  =_=  =_=  =_=  =_= 
Fatal Python error: _enter_buffered_busy: could not acquire lock for <_io.BufferedWriter name='<stderr>'> at interpreter shutdown, possibly due to daemon threads
Python runtime state: finalizing (tstate=0xd0c180)

Current thread 0x00007f08a638f700 (most recent call first):
<no Python frame>
Aborted (core dumped)
------------------------------------------------------------------------------

When I remove "time.sleep(0.1)" or  "thread.setDaemon(True)" or "sys.stderr.write(' =_= ')" or "for i in range(0,10000000)":, the python interpreter seems to work well.