I found out, that even pythontex may require rerun:
If there is code in caption of a floating object, say a figure,
then the pythontex package adds those not before the 2nd latex run
to the pytxcode file.
As floats may float,
the ordering of processing code, partially floating partially not,
may change and the results may be sensitive to that.
So if the pytxcode file changes,
so the program pythontex shall be rerun,
followed by at least one latex run.
This is very much parallel to makeindex and makeglossary.
I found out, that even pythontex may require rerun: If there is code in caption of a floating object, say a figure, then the pythontex package adds those not before the 2nd latex run to the pytxcode file. As floats may float, the ordering of processing code, partially floating partially not, may change and the results may be sensitive to that. So if the pytxcode file changes, so the program pythontex shall be rerun, followed by at least one latex run.
This is very much parallel to makeindex and makeglossary.