Cookbook
==========================

.. seealso:: :doc:`PyWebIO Battery <battery>`

.. contents::
   :local:

Interaction related
----------------------------------------------------------------------------------------------

Equivalent to "Press any key to continue"
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. exportable-codeblock::
    :name: cookbook-press-anykey-continue
    :summary: Press any key to continue

    actions(buttons=["Continue"])
    put_text("Go next")  # ..demo-only


Output pandas dataframe
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. exportable-codeblock::
    :name: cookbook-pandas-df
    :summary: Output pandas dataframe

    import numpy as np
    import pandas as pd

    df = pd.DataFrame(np.random.randn(6, 4), columns=list("ABCD"))
    put_html(df.to_html(border=0))

.. seealso:: `pandas.DataFrame.to_html — pandas documentation <https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.to_html.html#pandas-dataframe-to-html>`_

Output Matplotlib figure
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Instead of using ``matplotlib.pyplot.show()``, to show matplotlib figure in PyWebIO, you need to save the figure to in-memory buffer fist and then output the buffer
via :func:`pywebio.output.put_image`:

.. exportable-codeblock::
    :name: cookbook-matplotlib
    :summary: Output Matplotlib plot

    import matplotlib
    import matplotlib.pyplot as plt
    import io
    import pywebio

    matplotlib.use('agg')  # required, use a non-interactive backend

    fig, ax = plt.subplots()  # Create a figure containing a single axes.
    ax.plot([1, 2, 3, 4], [1, 4, 2, 3])  # Plot some data on the axes.

    buf = io.BytesIO()
    fig.savefig(buf)
    pywebio.output.put_image(buf.getvalue())

The ``matplotlib.use('agg')`` is required so that the server does not try to create (and then destroy) GUI windows
that will never be seen.

When using Matplotlib in a web server (multiple threads environment), pyplot may cause some conflicts in some cases,
read the following articles for more information:

    * `Multi Threading in Python and Pyplot | by Ranjitha Korrapati | Medium <https://medium.com/@ranjitha.korrapati/multi-threading-in-python-and-pyplot-46f325e6a9d0>`_

    * `Embedding in a web application server (Flask) — Matplotlib documentation <https://matplotlib.org/stable/gallery/user_interfaces/web_application_server_sgskip.html>`_


Add new syntax highlight for code output
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

When output code via `put_markdown()` or `put_code()`, PyWebIO provides syntax highlight for some common languages.
If you find your code have no syntax highlight, you can add the syntax highlighter by two following steps:

1. Go to `prismjs CDN page <https://www.jsdelivr.com/package/npm/prismjs?version=1.23.0&path=components>`_ to get your syntax highlighter link.
2. Use :func:`config(js_file=...) <pywebio.config>` to load the syntax highlight module

::

    @config(js_file="https://cdn.jsdelivr.net/npm/prismjs@1.23.0/components/prism-diff.min.js")
    def main():
        put_code("""
    + AAA
    - BBB
    CCC
        """.strip(), language='diff')

        put_markdown("""
        ```diff
        + AAA
        - BBB
        CCC
        ```
        """, lstrip=True)



Web application related
----------------------------------------------------------------------------------------------

Add Google AdSense/Analytics code
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

When you setup Google AdSense/Analytics, you will get a javascript file and a piece of code that needs to be inserted
into your application page, you can use :func:`pywebio.config()` to inject js file and code to your PyWebIO application::

    from pywebio import start_server, output, config

    js_file = "https://www.googletagmanager.com/gtag/js?id=G-xxxxxxx"
    js_code = """
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('js', new Date());

    gtag('config', 'G-xxxxxxx');
    """

    @config(js_file=js_file, js_code=js_code)
    def main():
        output.put_text("hello world")

    start_server(main, port=8080)


Refresh page on connection lost
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Add the following code to the beginning of your PyWebIO application main function::

    session.run_js('WebIO._state.CurrentSession.on_session_close(()=>{setTimeout(()=>location.reload(), 4000})')