.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        Click :ref:`here <sphx_glr_download_gallery_user_interfaces_web_application_server_sgskip.py>`     to download the full example code
    .. rst-class:: sphx-glr-example-title

    .. _sphx_glr_gallery_user_interfaces_web_application_server_sgskip.py:


=============================================
Embedding in a web application server (Flask)
=============================================

When using Matplotlib in a web server it is strongly recommended to not use
pyplot (pyplot maintains references to the opened figures to make
`~.matplotlib.pyplot.show` work, but this will cause memory leaks unless the
figures are properly closed).

Since Matplotlib 3.1, one can directly create figures using the `.Figure`
constructor and save them to in-memory buffers.  In older versions, it was
necessary to explicitly instantiate an Agg canvas (see e.g.
:doc:`/gallery/user_interfaces/canvasagg`).

The following example uses Flask_, but other frameworks work similarly:

.. _Flask: https://flask.palletsprojects.com


.. code-block:: default


    import base64
    from io import BytesIO

    from flask import Flask
    from matplotlib.figure import Figure

    app = Flask(__name__)


    @app.route("/")
    def hello():
        # Generate the figure **without using pyplot**.
        fig = Figure()
        ax = fig.subplots()
        ax.plot([1, 2])
        # Save it to a temporary buffer.
        buf = BytesIO()
        fig.savefig(buf, format="png")
        # Embed the result in the html output.
        data = base64.b64encode(buf.getbuffer()).decode("ascii")
        return f"<img src='data:image/png;base64,{data}'/>"


Since the above code is a Flask application, it should be run using the
`flask command-line tool <https://flask.palletsprojects.com/en/master/cli/>`_
Assuming that the working directory contains this script:

Unix-like systems

.. code-block:: console

 FLASK_APP=web_application_server_sgskip flask run

Windows

.. code-block:: console

 set FLASK_APP=web_application_server_sgskip
 flask run


Clickable images for HTML
-------------------------

Andrew Dalke of `Dalke Scientific <http://www.dalkescientific.com>`_
has written a nice `article
<http://www.dalkescientific.com/writings/diary/archive/2005/04/24/interactive_html.html>`_
on how to make html click maps with Matplotlib agg PNGs.  We would
also like to add this functionality to SVG.  If you are interested in
contributing to these efforts that would be great.


.. _sphx_glr_download_gallery_user_interfaces_web_application_server_sgskip.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download sphx-glr-download-python

     :download:`Download Python source code: web_application_server_sgskip.py <web_application_server_sgskip.py>`



  .. container:: sphx-glr-download sphx-glr-download-jupyter

     :download:`Download Jupyter notebook: web_application_server_sgskip.ipynb <web_application_server_sgskip.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    Keywords: matplotlib code example, codex, python plot, pyplot
    `Gallery generated by Sphinx-Gallery
    <https://sphinx-gallery.readthedocs.io>`_