Decode zip/base64 file as a PDF file in response in Python (Django), why my PDF is blank?

Question

I have zip/base64 data string. First, I tried to use base64 decode it. Then used zipfile in Python to unzip this file.

Then I put contents in response as a PDF file. I can see that the PDF I downloaded has 7 pages and length is about 75000. But all pages are blank. I wonder there is something wrong with decoding?

This .decode(errors='ignore') was from another stackoverflow post. Without this statement, I cannot decode the whole thing. It will pop error like "'utf-8' codec can't decode byte 0xfe in position 28".

Here is my code:

decoded = base64.b64decode(data) // data is "zip/base64" type

with zipfile.ZipFile(io.BytesIO(decoded)) as zf:
    for name in zf.namelist():
        with zf.open(name) as f:
            contents = f.read().decode(errors='ignore')

response = HttpResponse(
    contents, content_type="application/pdf"
)
response["Content-Disposition"] = 'attachment; filename="{}"'.format(
    report_name + ".pdf"
)
return response

Answer 1

You shouldn't try to decode the file contents, since it's not text. f.read() returns a bytestring, which HttpResponse will accept perfectly fine for the page content.