Debug Intermittent Calculator Bug

<context> I'm building a simple Python calculator application. It's a command-line interface (CLI) application for now, focusing on basic arithmetic operations. I'm using standard Python libraries and haven't implemented any complex error handling or UI yet. <problem> When I perform a simple addition, like '2 + 2', the calculator sometimes returns '5' instead of '4'. This doesn't happen consistently, but it's reproducible after a few calculations. It seems to be more frequent after performing a division operation. </problem> <goal> Identify the cause of this incorrect addition result and ensure that basic arithmetic operations, specifically addition, always return the correct value. I need to find the bug in my logic that's causing this intermittent incorrect calculation, possibly after a division. </goal> </context> <codebase> <file1> {{Your file 1 content}} </file1> <file2> {{Your file 2 content}} </file2> </codebase>