python-docx : adding checkbox to .docx doesn't work - python-3.x

Question

I want to add xml to my .docx document using python-docx library. I tried this code from stackoverflow but it doesn't work, I don't know why. I get nothing when opening the docx with LibreOffice and Microsoft word.
table = document.add_table(rows=1, cols=1)
p = table.cell(0, 0).paragraphs[0]
run = p.add_run()
tag = run._r
start = docx.oxml.shared.OxmlElement('w:bookmarkStart')
start.set(docx.oxml.ns.qn('w:id'), '0')
start.set(docx.oxml.ns.qn('w:name'), '0')
tag.append(start)
ctype = docx.oxml.OxmlElement('w:complexType')
ctype.set(docx.oxml.ns.qn('w:name'), 'CT_FFCheckBox')
seq = docx.oxml.OxmlElement('w:sequence')
choice = docx.oxml.OxmlElement('w:choice')
el = docx.oxml.OxmlElement('w:element')
el.set(docx.oxml.ns.qn('w:name'), 'size')
el.set(docx.oxml.ns.qn('w:type'), 'CT_HpsMeasure')
el2 = docx.oxml.OxmlElement('w:element')
el2.set(docx.oxml.ns.qn('w:name'), 'sizeAuto')
el2.set(docx.oxml.ns.qn('w:type'), 'CT_OnOff')
choice.append(el)
choice.append(el2)
el3 = docx.oxml.OxmlElement('w:element')
el3.set(docx.oxml.ns.qn('w:name'), 'default')
el3.set(docx.oxml.ns.qn('w:type'), 'CT_OnOff')
el3.set(docx.oxml.ns.qn('w:minOccurs'), '0')
el4 = docx.oxml.OxmlElement('w:element')
el4.set(docx.oxml.ns.qn('w:name'), 'checked')
el4.set(docx.oxml.ns.qn('w:type'), 'CT_OnOff')
el4.set(docx.oxml.ns.qn('w:minOccurs'), '0')
seq.append(choice)
seq.append(el3)
seq.append(el4)
ctype.append(seq)
start.append(ctype)
end = docx.oxml.shared.OxmlElement('w:bookmarkEnd')
end.set(docx.oxml.ns.qn('w:id'), '0')
end.set(docx.oxml.ns.qn('w:name'), '0')
tag.append(end)
Can you help me? Thank you very much
PS : I find the code here

Answer 1

Tweaking the function from this SO post, I got this to work.
import docx
import random
def addCheckbox(para, box_id, name):
run = para.add_run()
tag = run._r
fld = docx.oxml.shared.OxmlElement('w:fldChar')
fld.set(docx.oxml.ns.qn('w:fldCharType'), 'begin')
ffData = docx.oxml.shared.OxmlElement('w:ffData')
e = docx.oxml.shared.OxmlElement('w:name')
e.set(docx.oxml.ns.qn('w:val'), 'Check1')
ffData.append(e)
ffData.append(docx.oxml.shared.OxmlElement('w:enabled'))
e = docx.oxml.shared.OxmlElement('w:calcOnExit')
e.set(docx.oxml.ns.qn('w:val'), '0')
ffData.append(e)
e = docx.oxml.shared.OxmlElement('w:checkBox')
e.append(docx.oxml.shared.OxmlElement('w:sizeAuto'))
ee = docx.oxml.shared.OxmlElement('w:default')
ee.set(docx.oxml.ns.qn('w:val'), '0')
e.append(ee)
ffData.append(e)
fld.append(ffData)
tag.append(fld)
run2 = para.add_run()
tag2 = run2._r
start = docx.oxml.shared.OxmlElement('w:bookmarkStart')
start.set(docx.oxml.ns.qn('w:id'), str(box_id))
start.set(docx.oxml.ns.qn('w:name'), name)
tag2.append(start)
run3 = para.add_run()
tag3 = run3._r
instr = docx.oxml.OxmlElement('w:instrText')
instr.text = 'FORMCHECKBOX'
tag3.append(instr)
run4 = para.add_run()
tag4 = run4._r
fld2 = docx.oxml.shared.OxmlElement('w:fldChar')
fld2.set(docx.oxml.ns.qn('w:fldCharType'), 'end')
tag4.append(fld2)
run5 = para.add_run()
tag5 = run5._r
end = docx.oxml.shared.OxmlElement('w:bookmarkEnd')
end.set(docx.oxml.ns.qn('w:id'), str(box_id))
end.set(docx.oxml.ns.qn('w:name'), name)
tag5.append(end)
if __name__ == '__main__':
document = docx.Document()
document.add_heading('Document Title', 0)
p1 = document.add_paragraph('A paragraph with a checkbox ')
addCheckbox(p1, random.randint(16*1024, 32*1024), 'justinwashere')
document.save('demo.docx')
I changed the contents of his ffData in the function to match the replacement XML in his original question.