Generate XFDF file for filling a PDF Form (Python 3.x)

generateXFDF.py

def generateXFDF(valueMap, path):
    # Convert map of values into a tree of values
    valueTree = {}
    for fieldPath, value in valueMap.items():
        tr = valueTree
        segs = fieldPath.split('.')
        for seg in segs[:-1]:
            if seg not in tr: tr[seg] = {}
            tr = tr[seg]
        tr[segs[-1]] = value

    with open(path, 'w', encoding='utf-8') as f:
        def writeDict(d, indent):
            for field, val in d.items():
                f.write('\t'*indent + '<field name="' + field + '">\n')
                if isinstance(val, dict):
                    writeDict(val, indent+1)
                else:
                    f.write('\t'*(indent+1) + '<value>' + val + '</value>\n')
                f.write('\t'*indent + '</field>\n')
        f.write('<?xml version="1.0" encoding="UTF-8"?>\n')
        f.write('<xfdf xmlns="http://ns.adobe.com/xfdf/" xml:space="preserve">\n')
        f.write('<fields>\n')
        writeDict(valueTree, 0)
        f.write('</fields>\n')
        f.write('</xfdf>\n')

if __name__ == '__main__':
    # Here is how to use the function:
    valueMap = {
        'topmostSubform[0].Page1[0].NameAndAddress1[0].f1_1[0]': 'Joe Doe',
        'topmostSubform[0].Page1[0].NameAndAddress1[0].f1_2[0]': '1234 Main Street',
        'topmostSubform[0].Page1[0].NameAndAddress1[0].f1_3[0]': 'Bluetown, BL',
        'topmostSubform[0].Page1[0].f1_19[0]': 'Goldman Sachs US Equity',
        'topmostSubform[0].Page1[0].f1_20[0]': '2018-04-15',
        'topmostSubform[0].Page1[0].f1_21[0]': '200'
    }
    generateXFDF(valueMap, 'test.xfdf')

    # Fill the form, if you want to do it from Python:
    import subprocess
    subprocess.run(['pdftk', 'form.pdf',
                    'fill_form', 'test.xfdf',
                    'output', 'filledForm.pdf']).check_returncode()