Hello valeriymartsyshyn,

This is for reporting bugs in the Python interpreter, it is not a help desk for learning how to program in Python. There are many places you can ask for help to debug your code, such as Reddit's r/learnpython, or Stackoverflow, or the tutor mailing list:

https://mail.python.org/mailman/listinfo/tutor

There are various Python IRC channels or Discuss, if you google you will soon find them.

In this case, your bug occurs because you are deleting items from the list as you are iterating over it. Don't do that.