save 3d transient binary array to .hds format

[RyanConway91]

I am using the API to create a custom package. A result of this package is a 3D transient array (so 4D I guess...) of dimensions:
[kper*kstp, nlay, nrow, ncol]

From an example notebook, I figured out how to save a 2D array (layer 1 of last kstp,kper) to binary:

aa = d_as[list(d_as.keys())[-1]]#tr 3D of calculcated CO2 thickness
text = "co2_thick"
ilay = 1#not 0 based!
pertim = dt
totim = current_time
kper = kper+1#not 0 based!
kstp = kstp+1#not 0 based!
header = fp.utils.BinaryHeader.create(bintype="head", precision="double",
                                         text=text, nrow=mg.nrow, ncol=mg.ncol,
                                         ilay=1, pertim=pertim,
                                         totim=pertim, kstp=kstp, kper=kper)
fp.utils.Util2d.write_bin(b.shape, "co2_thick.hds", aa, header_data=header)

How can I extend this to transient 3d/4d?

[RyanConway91]

Figured it out...

def write_4d_binary(d_as,fb_out,fb_ref_hd):
    '''
    function to write binary 4D (transient 3D) array using a refernce binary .hds file
    ----------
    Parameters
    ----------
    d_as : dictionary
        {idx:3D np.array()} of values. Could also be 4D np array?
    fb_out : str
        file path of binary file to write.Extension can be anything. Use .hds 
        to make loading into GUIs easier
    fb_ref_hd : str
        file path of reference binary heads. 

    '''
    h_ref = fp.utils.binaryfile.HeadFile(fb_ref_hd)
    nrecords = h_ref.recordarray.shape[0]
    with open(fb_out, "wb") as fbin:
        for idx in range(nrecords):
            header = h_ref.recordarray[idx].copy()
            h = np.array(header, dtype=np.dtype(header))
            h.tofile(fbin)
            data = np.array(d_as[idx], dtype=np.float64)
            data.tofile(fbin)
            
fb_ref_hd = r'{}\{}'.format(sim_ws,'it_gwf_base.hds')
fb_out = r'{}\{}'.format(sim_ws,'CO2_thickness.hds')# file
write_4d_binary(d_as,fb_out,fb_ref_hd)

This function uses a reference .hds file so it assumes you saved every kstp,kper you want in the new binary file to that file