How do I properly implement Shiny for Python Modules in Quarto?

[mortonanalytics]

Description

I'm attempting to use Shiny for Python modules in a Quarto Dashboard. It needs access to the session to run properly. I'm looking for guidance or examples of using Shiny for Python modules in Quarto Dashboard. The UI portion of the module runs, but I can't seem to get the server function to run as it needs access to the Shiny session.

Main qmd:

---
title: "Shiny Modules"
format: dashboard
server: shiny
---

```{python}
from shiny import module, ui, render, reactive, event, session
from modules.map_view import counter_ui, counter_server
```

# Map View

## Column

```{python}
counter_ui("counter1", "Counter 1")
```

```{python}
counter_server("counter1", starting_value=5)
```

map_view.py:

from shiny import module, ui, render, reactive, event

@module.ui
def counter_ui(label: str = "Increment counter"):
    return ui.card(
        ui.card_header("This is " + label),
        ui.input_action_button(id="button", label=label),
        ui.output_code(id="out"),
    )


@module.server
def counter_server(input, output, session, starting_value = 0):
    count =  reactive.value(starting_value)

    @reactive.effect
    @reactive.event(input.button)
    def _():
        count.set(count() + 1)

    @render.code
    def out():
        return f"Click count is {count()}"

[mcanouil]

Could you properly format your post using code blocks for code and terminal outputs? Thanks.
If your code contains code blocks, you need to enclose it using more backticks, i.e., usually four ````.
See https://quarto.org/bug-reports.html#formatting-make-githubs-markdown-work-for-us.

Did you take a look at the documentation? https://quarto.org/docs/dashboards/interactivity/shiny-python/index.html

[mortonanalytics]

Updated.

Yes, I've read and re-read the docs multiple times and it does not use modules for code examples or reference their usage. Also, it's not clear to me how modules in Shiny for R would work in Quarto Dashboards either.

What I'm trying to understand is how the session object gets passed to modules in a Quarto Dashboard format using a shiny runtime. I previously tried building a traditional server function inside a code chunk to call the modules, but that left a spinning wheel that never ended for the above example - a counter. It seemed like that was close, but not firing all the way.

I then attempted to assign a session object and pass that to the module, but that threw an error that session was an unknown object (paraphrasing a bit there).

I think it's 100%b reasonable if "Shiny modules aren't intended for Quarto interactive Dashboards in either R or Python." But I don't see docs or discussion saying it's not possible.

[mcanouil]

Note that your code seems off: for instance why do you have a backtick before @module?

Did you try your code outside of Quarto as a regular Shiny app? Does it work?
Have you looked at the Shiny documentation? https://shiny.posit.co/py/docs/

[mortonanalytics]

I removed the back tick in editing.

yes, the app works fine - it's just the example app from the Shiny for Python docs I tried to convert to Quarto using modules.

Yes, I've read the docs - I don't know how to make that more clear. I've worked with Shiny for R for over 10 years and use the Shiny for Python constantly docs to transfer my knowledge into code for my current Python project. I've moved on and will finish this project without Quarto. I'll give it another try when I have more time.

[mcanouil]

Is your issue the following error?

RuntimeError: wrapper() must be called from within an active Shiny session.

If so, there might be something missing in either or both Quarto and Shiny.

edit: here is what I've tried from https://shiny.posit.co/py/docs/modules.html#how-to-use-modules

---
title: "Shiny Modules"
format: html
server: shiny
---

```{python}
from shiny.express import module, render, ui

@module
def io_row(input, output, session, placeholder=""):
    with ui.layout_columns():
        with ui.card():
            ui.input_text(f"text_input", "Enter text", placeholder=placeholder)
        with ui.card():
            @render.text
            def text_out():
                return f'You entered "{input.text_input()}"'


extra_ids = ["row_3", "row_4", "row_5"]

io_row("row_1")
# Call with a different ID and pass in argument for placeholder
io_row("row_2", placeholder="Enter second thing")
# We can add more instances programmatically
[io_row(x) for x in extra_ids]
```

which lead to:

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[1], line 16
     11                 return f'You entered "{input.text_input()}"'
     14 extra_ids = ["row_3", "row_4", "row_5"]
---> 16 io_row("row_1")
     17 # Call with a different ID and pass in argument for placeholder
     18 io_row("row_2", placeholder="Enter second thing")

File ~/Projects/quarto/quarto-playground/.venv/lib/python3.13/site-packages/shiny/express/_module.py:47, in module.<locals>.wrapper(id, *args, **kwargs)
     45 @functools.wraps(fn)
     46 def wrapper(id: Id, *args: P.args, **kwargs: P.kwargs) -> R:
---> 47     parent_session = require_active_session(None)
     48     module_session = parent_session.make_scope(id)
     50     with session_context(module_session):

File ~/Projects/quarto/quarto-playground/.venv/lib/python3.13/site-packages/shiny/session/_utils.py:129, in require_active_session(session)
    124     if calling_fn_name == "__init__":
    125         # If the caller is __init__, then we're most likely in the initialization of
    126         # an object. This will get the class name.
    127         calling_fn_name = caller.frame.f_locals["self"].__class__.__name__
--> 129     raise RuntimeError(
    130         f"{calling_fn_name}() must be called from within an active Shiny session."
    131     )
    132 return session

RuntimeError: wrapper() must be called from within an active Shiny session.

ERROR: Error
    at renderFiles (file:///Users/mcanouil/Projects/quarto/quarto-cli/src/command/render/render-files.ts:350:23)
    at eventLoopTick (ext:core/01_core.js:175:7)
    at async render (file:///Users/mcanouil/Projects/quarto/quarto-cli/src/command/render/render-shared.ts:104:18)
    at async renderForPreview (file:///Users/mcanouil/Projects/quarto/quarto-cli/src/command/preview/preview.ts:428:24)
    at async render (file:///Users/mcanouil/Projects/quarto/quarto-cli/src/command/preview/preview-shiny.ts:65:22)
    at async previewShiny (file:///Users/mcanouil/Projects/quarto/quarto-cli/src/command/preview/preview-shiny.ts:78:18)
    at async Command.actionHandler (file:///Users/mcanouil/Projects/quarto/quarto-cli/src/command/preview/cmd.ts:304:28)
    at async Command.execute (https://deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1948:7)
    at async Command.parseCommand (https://deno.land/x/cliffy@v1.0.0-rc.3/command/command.ts:1780:14)
    at async quarto (file:///Users/mcanouil/Projects/quarto/quarto-cli/src/quarto.ts:190:5)

[mcanouil]

I think the issue is the rendering step because modules cannot be executed outside of a running application (you can get eh above message, by simply executing the code in a Python console). So when quarto render is ran, it crashes even before the app is ran (https://quarto.org/docs/dashboards/interactivity/shiny-python/running.html).

[mcanouil]

FYI, I have opened an issue about the use of modules (can't tell if the issue is completely on Quarto CLI and/or shiny):

• Fail to render shiny-based document with modules #12210

[mortonanalytics]

I'll pursue the question elsewhere. Thanks for your time.

[mcanouil]

Just in case, when using server: shiny you need to use quarto serve. (There were reports of issue when using quarto preview)

[wch]

I wrote up an explanation and provided a workaround here: #12210 (comment)

The workaround is basically to write Shiny Core code.