Pandas Dataframes to Fortran Formatting

Ahhhh, Fortran.

The past few weeks I’ve had the pleasure (I think that’s the right word?) of dusting off my olde Fortran skills for several unrelated projects, one of which requires exporting of a pandas dataframe from python to a plain text CSV readable by some legacy fortran code. We wanted to speed up and simplify that code, and in the end I figured out a neat way to do it. The solutions out on the web (e.g., this SO post) generally follow the approach of iterating over every row in the dataframe, writing out each row with the appropriate formatting. While the pandas.DataFrame.to_csv() function has an option to format columns, it applies that formatting to every column and we need individual control.

So here’s a notebook (available over at github as well) to help out anyone out using python and fortran in tandem! It makes use of the lovely fortranformat package so that you can use your beloved fortran format strings exactly as you do in fortran!