[Python] Module not found when using UV, py-shiny and external dependency

I want to create a shiny app (using py-shiny) where I manage the dependencies using uv.

So far I have used the following code

uv init shiny-tester
cd shiny-tester
uv add shiny
vim app.py # see below
uvx shiny run # works as expected


where I write the following to app.py (directly taken from the official doc):

from shiny import App, reactive, render, ui

# will be used later
# import numpy

app_ui = ui.page_fluid(
ui.input_action_button("action_button", "Action"),
ui.output_text("counter"),
)

def server(input, output, session):
@render.text()
@reactive.event(input.action_button)
def counter():
return f"{input.action_button()}"

app = App(app_ui, server)


This works as expected using uvx shiny run and the app runs.

When I try to add any other package, eg numpy by inserting a import numpy into app.py, I get the error that the module could not be found because I didnt install it yet. To fix this I run uv add numpy, which works and does not throw any errors.

When I run uvx shiny run however, I still get the error

File "/mnt/c/Users/david/Desktop/shiny-tester/app.py", line 2, in <module>
import numpy
ModuleNotFoundError: No module named 'numpy'


When I run uv run python and import numpy the module can be found and loaded.

Any idea what might cause this and how to fix it?

Version etc


❯ uv --version
uv 0.4.17
❯ cat pyproject.toml
[project]
name = "shiny-tester"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
"numpy>=2.1.1",
"shiny>=1.1.0",
]

❯ head uv.lock
version = 1
requires-python = ">=3.12"
resolution-markers = [
"platform_system != 'Emscripten'",
"platform_system == 'Emscripten'",
]

[[package]]
name = "anyio"
version = "4.6.0"

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