How to edit editable pdf using the pdfrw library?

Question

I been doing research on how to edit PDF using Python and i have found this article:
How to Populate Fillable PDF\'s with Python

However there is a problem on

Answer 1

The error is because no appearance stream is associated with the field, but you've created it in a wrong way. You've just assigned and stream to AP dictionary. What you need to do is to assign an indirect Xobject to /N in /AP dictionary; and you need to crate Xobject from scratch. The code should be something like the following:

from pdfrw import PdfWriter, PdfReader, IndirectPdfDict, PdfName, PdfDict

INVOICE_TEMPLATE_PATH = 'untitled.pdf'
INVOICE_OUTPUT_PATH = 'untitled-output.pdf'

field1value = 'im field_1 value'

template_pdf = PdfReader(INVOICE_TEMPLATE_PATH)
template_pdf.Root.AcroForm.Fields[0].V = field1value

#this depends on page orientation
rct = template_pdf.Root.AcroForm.Fields[0].Rect
hight = round(float(rct[3]) - float(rct[1]),2)
width =(round(float(rct[2]) - float(rct[0]),2)

#create Xobject
xobj = IndirectPdfDict(
            BBox = [0, 0, width, hight],
            FormType = 1,
            Resources = PdfDict(ProcSet = [PdfName.PDF, PdfName.Text]),
            Subtype = PdfName.Form,
            Type = PdfName.XObject
            )

#assign a stream to it
xobj.stream = '''/Tx BMC
BT
 /Helvetica 8.0 Tf
 1.0 5.0 Td
 0 g
 (''' + field1value + ''') Tj
ET EMC'''

#put all together
template_pdf.Root.AcroForm.Fields[0].AP = PdfDict(N = xobj)

#output to new file
PdfWriter().write(INVOICE_OUTPUT_PATH, template_pdf)

Note: FYI: /Type, /FormType, /Resorces are optional (/Resources is strongly recomended).

Answer 2

Updating the write function to have keys AP and V fixed the problem for me in preview

pdfrw.PdfDict(AP=data_dict[key], V=data_dict[key])

Answer 3

I figure out that if you add NeedAppearances param you will solve your problem:

template_pdf = pdfrw.PdfReader(TEMPLATE_PATH)
template_pdf.Root.AcroForm.update(pdfrw.PdfDict(NeedAppearances=pdfrw.PdfObject('true'))) 

Answer 4

To expand on Sergio's answer above, the following line:

template_pdf.Root.AcroForm.update(pdfrw.PdfDict(NeedAppearances=pdfrw.PdfObject('true')))

Should be put after this line in the example code from OP:

template_pdf = pdfrw.PdfReader(input_pdf_path)