I need to programmatically fill out a PDF form's radio buttons, can I do this in JS, go, or python?

I found pdf-fill-form for node.js and am using that well for filling out a PDF application that a client needs to match the user's online application. The only issue is that the pdf has a few radio buttons, like for gender, and I get no response when I try and set the field "Sex" value to "Male" or "Female" even though those are the values.

  var vals = {"Sex": "Male"}

  pdfFillForm.write(sourcePDF, vals, { "save": "pdf" } )
    .then(function(result) {
      fs.writeFile(destinationPDF, result, function(err){
        if (err) {
          return console.log(err);
        }
        console.log("Success Saving");
      });
    }, function(err) {
      console.log(err);
  });

It says clearly in pdf-fill-form documentation that it only supports text and checkboxes so I get it, but I can't find anything outside of Java or C#/C++ that can do this, and I really don't want to add another technology to solve what seems like a fairly common problem. Anyone know of anything? Or is there a work around? Thanks.

I made the fix myself, actually wasn't to bad. I just updated the pdf-fill-form code, and am waiting to hear back about my pull request, but if anyone needs it in the meantime, https://github.com/mttchrry/pdf-fill-form

My solution for python using pypdftk

Input PDF file

The pdf file is created in LibreOffice Draw, using the File/Export As/Export as PDF..

The radio buttons of a group all have the same name, and no group name.
(It seems you get the same result if setting different names and the same group name)

On a machine having pdftk installed, run the following on your input pdf file containing at least two radio buttons in a group:

pdftk in.pdf dump_data_fields > fields.list

File fields.list should have a section like:

FieldType: Button
FieldName: radio_button_cooking
FieldFlags: 49152
FieldValue: 1
FieldValueDefault: Off
FieldJustification: Left
FieldStateOption: 1
FieldStateOption: 2
FieldStateOption: 3
FieldStateOption: Off

Meaning there are two buttons in the group, with the same name radio_button_cooking.
If you have more buttons in the group, the values continue with 4, ..

Fill the PDF using pypdftk

Possible values for the buttons are here either 1, 3, or 3. Or nothing for no selection.

import pypdftk

val_rare = 1 #guesswork to link values to options
val_medium = 2
val_welldone = 3
fields = {
    'my_radio_button': val_medium,
}
pypdftk.fill_form("in.pdf", fields, "out.pdf", flatten=False)

File out.pdf should now have one of both radio buttons selected.
You have to do some guesswork to find out which button has value 1, 2 and 3.

If you don't want to use pypdftk, there are other options.