When building IoT dashboards, hardware monitoring systems, or data logging tools, a common requirement is running a background task—like listening to a serial port or running a continuous while loop—alongside a web application framework like Flask. However, many developers encounter an issue where Flask blocks the main execution thread, preventing the background loop from starting until the server shuts down.

The Core Problem: Function Invocation vs. Function Reference

In Python's threading module, passing a target function requires passing a reference to the function itself, rather than executing the function directly. Consider the following common mistake: