I\'ve been documenting a software package using Sphinx and reStructuredText.
Within my documents, there are some long code snippets. I want to be able to have them
I think the easiest way to do this would be to create a custom Sphinx theme in which you tell certain html elements to have this functionality. A little JQuery would go a long way here.
If, however you want to be able to specify this in your reStructuredText markup, you would need to either
This would be a bit more work, but would give you more flexibility.
There is a very simplistic extension providing exactly that feature: https://github.com/scopatz/hiddencode
It works rather well for me.
You can use the built-in HTML collapsible details tag by wrapping the code in two raw HTML directives
.. raw:: html
   <details>
   <summary><a>big code</a></summary>
.. code-block:: python
   lots_of_code = "this text block"
.. raw:: html
   </details>
Produces:
<details>
<summary><a>big code</a></summary>
<pre>lots_of_code = "this text block"</pre>
</details>
You don't need a custom theme. Use the built-in directive container that allows you to add custom css-classes to blocks and override the existsting theme to add some javascript to add the show/hide-functionality.
This is _templates/page.html:
{% extends "!page.html" %}
{% block footer %}
 <script type="text/javascript">
    $(document).ready(function() {
        $(".toggle > *").hide();
        $(".toggle .header").show();
        $(".toggle .header").click(function() {
            $(this).parent().children().not(".header").toggle(400);
            $(this).parent().children(".header").toggleClass("open");
        })
    });
</script>
{% endblock %}
This is _static/custom.css:
.toggle .header {
    display: block;
    clear: both;
}
.toggle .header:after {
    content: " ▶";
}
.toggle .header.open:after {
    content: " ▼";
}
This is added to conf.py:
def setup(app):
    app.add_css_file('custom.css')
Now you can show/hide a block of code.
.. container:: toggle
    .. container:: header
        **Show/Hide Code**
    .. code-block:: xml
       :linenos:
       from plone import api
       ...
I use something very similar for exercises here: https://training.plone.org/5/mastering-plone/about_mastering.html#exercises
The cloud sphinx theme has custom directive html-toggle that provides toggleable sections. To quote from their web page:
You can mark sections with
.. rst-class:: html-toggle, which will make the section default to being collapsed under html, with a “show section” toggle link to the right of the title.
Here is a link to their test demonstration page.