How to write external binary files without using flopy?

[hjia1005]

I am working on a big model. To rewrite the model files during calibration takes very long even when using external txt files. Also, I am using f.write() to write all model files to avoid calling Flopy which takes even longer to load up the model. I am planning to write external files in binary format, but very new to binary. Below is what I tried but mf6 doesn't recognise them.

Is there a way that I can write these binary files properly without calling Flopy to load my model? I checked the function write_binary_file( ) under class MFFileAccessList(MFFileAccess), seems it needs all the model information (such as header and modelgrid) to be read and then write the binary file. However, I don't need that information when writing external txt files, thinking it should also be possible to write the binary files in the same way.

Any assistance will be appreciated.

[hjia1005]

I think this explains how to do it. Will try.
[](modflowpy/flopy#470

[hjia1005]

Both grid data and list data are worked out. Binary grid data needs a header but list data for boundary packages doesn't need the header.