[Python] Download Reportlab PDF only when the user clicks a button

I'm trying to figure out how to only generate the PDF from Reportlab when the user clicks a Download button, instead of it automatically generating in my local folder. It is a streamlit application FYI.

Here is the code I have to set up the PDF and memory.

buffer = io.BytesIO()

doc = canvas.Canvas(buffer, pagesize=letter)

elements = []

# Add simple text to PDF
pdf_title = "Results"
title_paragraph = Paragraph(pdf_title, getSampleStyleSheet()['Title'])

# Add PDF title to PDF
elements.append(title_paragraph)


And here's the code I'm using to try to build the PDF and download it via a button. This is where I'm running into errors.

doc.showPage()

# Save the PDF
doc.save()
buffer.seek(0)

def getpdf():
response = HttpResponse(buffer, content_type='application/pdf')
response['Content-Disposition'] = 'attachment; filename="ClassificationResults"'.format("ClassificationResults.pdf")
return response

st.download_button("Download Results", downloadable_pdf, file_name='ClassificationResults', help=None, on_click="rerun",
type="secondary", icon=None, disabled=False, use_container_width=False)


I'm getting this error: RuntimeError: Invalid binary data format: <class 'django.http.response.HttpResponse'>

So I believe the issue is with the getpdf() function but I got that code from another stack overflow example and I'm not sure how to troubleshoot. Any help would be greatly appreciated!

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