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I think the variables x and y should point to the same value and their addresses are the same, but the global Frame shows different values in the picture. I don’t know whether I understand it wrongly or if there is a bug in Python Tutor.

I think the variables x and y should points the same value 4, and when x += 1, it will create a new value which stores 5 in Objects side, the variable x points to the value