My simple notepad code with QtWidgets.QPlainTextEdit() give me a crash dump on Linux Fedora 30 with python3

Python 3.7.4 (default, Jul  9 2019, 16:32:37) 
[GCC 9.1.1 20190503 (Red Hat 9.1.1-1)] on linux

[mythcat@desk pyqt5_examples]$ uname -a
Linux desk 5.3.7-200.fc30.x86_64 #1 SMP Fri Oct 18 20:13:59 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

[mythcat@desk pyqt5_examples]$ python3 notepad.py 

** (python3:3077): WARNING **: 11:26:06.007: AT-SPI: Could not obtain desktop path or name


** (python3:3077): WARNING **: 11:26:06.029: atk-bridge: GetRegisteredEvents returned message with unknown signature

** (python3:3077): WARNING **: 11:26:06.029: atk-bridge: get_device_events_reply: unknown signature

** (python3:3077): WARNING **: 11:26:06.029: atk-bridge: get_device_events_reply: unknown signature
Traceback (most recent call last):
  File "notepad.py", line 222, in assign_syntax_py
    self.syntax = mytext(self.text_widget.document())
NameError: name 'mytext' is not defined
Traceback (most recent call last):
  File "notepad.py", line 222, in assign_syntax_py
    self.syntax = mytext(self.text_widget.document())
NameError: name 'mytext' is not defined
Aborted (core dumped)

The code is self.syntax = my_notepad.mytext(self.text_widget.document())

Can you please attach a simple reproducer script without any third party modules like qtwidgets to ensure crash is due to CPython and not due to the code in third party module itself.

No. I don't have a reproducer script for this issue with Linux OS.
The mytext is a class from another script named my_notepad.
The problem comes with time when I use the menu to change the syntax value, as you can see:
self.syntax = mytext(self.text_widget.document())
My code is based on this example from GitHub account lfsando: https://github.com/lfsando/notepad/blob/master/highlighter.py maybe has the same error.

Python 3.7 is no longer maintained. If you are still seeing crashes in a current version (>= 3.9) then please create a new issue.

However, note that a bug report is more likely to get attention if it shows a bug in python, rather than just reporting that a complicated a system built on top of python is crashing.