Visual Studio Prebuild Event Does Not Write to Output Window Until Completed

Question

I am invoking a python script from a pre-build event as follows: py -3 "$(SolutionDir)/build.py"

Now the problem is that the script output is not written to the output window in the visual studio until the script is completed. The script may take several minutes on first run, so I would like to see what it is working on.

Is there a way to update the output window with script output?