Shiny express app with trailing comma shows weird text output

[gshotwell]

Instead of erroring this says:

(<div class="form-group shiny-input-container">
  <label class="control-label" id="n-label" for="n">Number of rows to display</label><input id="n" type="number" class="shiny-input-number form-control" value="20"/>
</div>,)

https://shinylive.io/py/editor/#code=NobwRAdghgtgpmAXGKAHVA6VBPMAaMAYwHsIAXOcpMAMwCdiYACAZwAsBLCbJjmVYnTJM6cKITIcAbnDwjKAEzh05AVw4AdCHwFCmqKBAVQWTE-oVb6jVp24Y4AD1SiWpnYOFdUqsnIA2UNjEvlphEOoY3r4A+hHwdByEABQakGlyaQByqjAARspMxDQixADupmTETAocLKiB2BlMAEwADACUeOFaAAKiRsoYxmRQMfSwcExaSiWolADm6hAsMQo0yR2IWky7NSUAvBYYACJQowBidJPJIDt7DwDkAIKPiEzAAIxyLXIAzABdboQB5PABCbw+ABY5ABWOQANiB91BTEeAGFIcAAOxyAAccgAnACUUwAL4dUmiMiqOgg9ZgMkAoA

[wch]

I see what the problem is. This is the line in question:

ui.input_numeric("n", "Number of rows to display", 20),

In Python, the trailing comma there is shorthand for a creating a tuple with just one element, so that line is equivalent to:

(ui.input_numeric("n", "Number of rows to display", 20), )

So it's not Shiny doing anything weird here -- it's just Python itself supporting a strange syntax.

---

Full app for reference:

from shiny import reactive, render, ui
import pandas as pd
from shiny.express import input, layout


ui.input_numeric("n", "Number of rows to display", 20),


@render.data_frame 
def penguins_df():
    df = pd.DataFrame({
        'A': [1, 2, 3],
        'B': [4, 5, 6],
        'C': [7, 8, 9]
    })
    return df