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123 lines
4.2 KiB
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123 lines
4.2 KiB
Plaintext
=======================
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How to create PDF files
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=======================
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This document explains how to output PDF files dynamically using Django views.
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This is made possible by the excellent, open-source ReportLab_ Python PDF
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library.
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The advantage of generating PDF files dynamically is that you can create
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customized PDFs for different purposes -- say, for different users or different
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pieces of content.
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For example, Django was used at kusports.com_ to generate customized,
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printer-friendly NCAA tournament brackets, as PDF files, for people
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participating in a March Madness contest.
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.. _ReportLab: https://docs.reportlab.com/
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.. _kusports.com: https://www2.kusports.com/
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Install ReportLab
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=================
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The ReportLab library is :pypi:`available on PyPI <reportlab>`. A `user guide`_
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(not coincidentally, a PDF file) is also available for download.
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You can install ReportLab with ``pip``:
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.. console::
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$ python -m pip install reportlab
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Test your installation by importing it in the Python interactive interpreter:
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.. code-block:: pycon
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>>> import reportlab
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If that command doesn't raise any errors, the installation worked.
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.. _user guide: https://www.reportlab.com/docs/reportlab-userguide.pdf
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Write your view
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===============
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The key to generating PDFs dynamically with Django is that the ReportLab API
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acts on file-like objects, and Django's :class:`~django.http.FileResponse`
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objects accept file-like objects.
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Here's a "Hello World" example::
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import io
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from django.http import FileResponse
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from reportlab.pdfgen import canvas
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def some_view(request):
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# Create a file-like buffer to receive PDF data.
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buffer = io.BytesIO()
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# Create the PDF object, using the buffer as its "file."
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p = canvas.Canvas(buffer)
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# Draw things on the PDF. Here's where the PDF generation happens.
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# See the ReportLab documentation for the full list of functionality.
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p.drawString(100, 100, "Hello world.")
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# Close the PDF object cleanly, and we're done.
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p.showPage()
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p.save()
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# FileResponse sets the Content-Disposition header so that browsers
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# present the option to save the file.
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buffer.seek(0)
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return FileResponse(buffer, as_attachment=True, filename="hello.pdf")
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The code and comments should be self-explanatory, but a few things deserve a
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mention:
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* The response will automatically set the MIME type :mimetype:`application/pdf`
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based on the filename extension. This tells browsers that the document is a
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PDF file, rather than an HTML file or a generic
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:mimetype:`application/octet-stream` binary content.
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* When ``as_attachment=True`` is passed to ``FileResponse``, it sets the
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appropriate ``Content-Disposition`` header and that tells web browsers to
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pop-up a dialog box prompting/confirming how to handle the document even if a
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default is set on the machine. If the ``as_attachment`` parameter is omitted,
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browsers will handle the PDF using whatever program/plugin they've been
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configured to use for PDFs.
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* You can provide an arbitrary ``filename`` parameter. It'll be used by browsers
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in the "Save as..." dialog.
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* You can hook into the ReportLab API: The same buffer passed as the first
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argument to ``canvas.Canvas`` can be fed to the
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:class:`~django.http.FileResponse` class.
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* Note that all subsequent PDF-generation methods are called on the PDF
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object (in this case, ``p``) -- not on ``buffer``.
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* Finally, it's important to call ``showPage()`` and ``save()`` on the PDF
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file.
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.. note::
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ReportLab is not thread-safe. Some of our users have reported odd issues
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with building PDF-generating Django views that are accessed by many people
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at the same time.
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Other formats
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=============
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Notice that there isn't a lot in these examples that's PDF-specific -- just the
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bits using ``reportlab``. You can use a similar technique to generate any
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arbitrary format that you can find a Python library for. Also see
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:doc:`/howto/outputting-csv` for another example and some techniques you can use
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when generated text-based formats.
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.. seealso::
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Django Packages provides a `comparison of packages
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<https://djangopackages.org/grids/g/pdf/>`_ that help generate PDF files
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from Django.
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