As mentioned in this
that I made, you cannot debug URL routes in Flask using PythonTools.
The debugger hits breakpoints before the call to app.run(), but in a decorated routing function, no breakpoints will be hit, meaning flask effectively cannot be debugged.
While I posted this when PT was still in version 2.0, this is still true for a Flask project made with PT 2.1
After reading some other responses on this issues page, breakpoints
get hit if you manually attach the VS debugger to the second instance of python.exe after you run the project. However this is fairly inconvenient as you have to re-attach each time you restart the project