Diagnostic files
Python logs a considerable amount of information as it runs. Some of this information is printed to the screen but a much more voluminous version of progress of the program is placed in a sub-directory, named diag_whatever, where whatever is the root name of the model being run.
In this directory one will find log files, e.g. whatever_0.diag, whatever_1.diag, and so on, where the in a multiprocessor run, the number refers to the log of a specific thread.
Inspecting these logs is important for understanding whether a Python run is successful, and for understanding why if failed if that is the case.