ui.table doesn't work with datetime datatypes

[zilch42]

Question

Hi there,

I believe ui.table suffers from the same issue that ui.aggrid did in #1698 before it got a fix. Should providing datetime values to ui.table work? I couldn't find any mention in the docs about allowed data types. Cheers

from nicegui import ui
import pandas as pd

df = pd.DataFrame({
    "Name": ["John", "Mary", "Peter"],
    "DOB": ["1/1/2000", "2/2/2002", "3/3/2003"],
})
df['DOB'] = pd.to_datetime(df['DOB'])


@ui.page('/')
def home():
    ui.table(
        columns=[{'name': col, 'label': col, 'field': col} for col in df.columns],
        rows=df.to_dict('records'),
    )

ui.run()

TypeError: Type is not JSON serializable: Timestamp

[phoskee]

This code converts date and time columns in the DataFrame to strings with the format 'YYYY-MM-DD HH:MM:SS' so that they can be serialized and displayed properly in the NiceGUI table.

df['DOB'] = df['DOB'].dt.strftime('%Y-%m-%d %H:%M:%S')

[zilch42]

Thanks @phoskee, I should have mentioned, I did figure out how to solve it eventually. My questions was more around whether ui.table should be capable of handling those datatypes, given aggrid was fixed to be able to do so. One argument for a fix is that the error message isn't very informative as to what's gone wrong. The full stack track doesn't suggest it's originated in ui.table at all.

Traceback (most recent call last):
  File "C:\Users\path\lib\site-packages\uvicorn\protocols\http\httptools_impl.py", line 435, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
  File "C:\Users\path\lib\site-packages\uvicorn\middleware\proxy_headers.py", line 78, in __call__
    return await self.app(scope, receive, send)
  File "C:\Users\path\lib\site-packages\fastapi\applications.py", line 292, in __call__
    await super().__call__(scope, receive, send)
  File "C:\Users\path\lib\site-packages\starlette\applications.py", line 122, in __call__
    await self.middleware_stack(scope, receive, send)
  File "C:\Users\path\lib\site-packages\starlette\middleware\errors.py", line 184, in __call__
    raise exc
  File "C:\Users\path\lib\site-packages\starlette\middleware\errors.py", line 162, in __call__
    await self.app(scope, receive, _send)
  File "C:\Users\path\lib\site-packages\starlette\middleware\base.py", line 108, in __call__
    response = await self.dispatch_func(request, call_next)
  File "C:\Users\path\lib\site-packages\nicegui\middlewares.py", line 10, in dispatch
    response = await call_next(request)
  File "C:\Users\path\lib\site-packages\starlette\middleware\base.py", line 84, in call_next
    raise app_exc
  File "C:\Users\path\lib\site-packages\starlette\middleware\base.py", line 70, in coro
    await self.app(scope, receive_or_disconnect, send_no_error)
  File "C:\Users\path\lib\site-packages\starlette\middleware\gzip.py", line 24, in __call__
    await responder(scope, receive, send)
  File "C:\Users\path\lib\site-packages\starlette\middleware\gzip.py", line 44, in __call__
    await self.app(scope, receive, self.send_with_gzip)
  File "C:\Users\path\lib\site-packages\starlette\middleware\exceptions.py", line 79, in __call__
    raise exc
  File "C:\Users\path\lib\site-packages\starlette\middleware\exceptions.py", line 68, in __call__
    await self.app(scope, receive, sender)
  File "C:\Users\path\lib\site-packages\fastapi\middleware\asyncexitstack.py", line 20, in __call__
    raise e
  File "C:\Users\path\lib\site-packages\fastapi\middleware\asyncexitstack.py", line 17, in __call__
    await self.app(scope, receive, send)
  File "C:\Users\path\lib\site-packages\starlette\routing.py", line 718, in __call__
    await route.handle(scope, receive, send)
  File "C:\Users\path\lib\site-packages\starlette\routing.py", line 276, in handle
    await self.app(scope, receive, send)
  File "C:\Users\path\lib\site-packages\starlette\routing.py", line 66, in app
    response = await func(request)
  File "C:\Users\path\lib\site-packages\fastapi\routing.py", line 273, in app
    raw_response = await run_endpoint_function(
  File "C:\Users\path\lib\site-packages\fastapi\routing.py", line 190, in run_endpoint_function
    return await dependant.call(**values)
  File "C:\Users\path\lib\site-packages\nicegui\page.py", line 112, in decorated
    return client.build_response(request)
  File "C:\Users\path\lib\site-packages\nicegui\client.py", line 97, in build_response
    elements = json.dumps({
  File "C:\Users\path\lib\site-packages\nicegui\json\orjson_wrapper.py", line 36, in dumps
    return orjson.dumps(obj, option=opts, default=_orjson_converter).decode('utf-8')
TypeError: Type is not JSON serializable: Timestamp

In the above example, my app file is called datetime_issue.py which isn't mentioned in the stack trace at all and I don't have any objects or columns called Timestamp so it can be difficult to identify the issue (unless of course someone finds this post :) ).

If it's not intended to work, that's fine. Just thought it was worth raising since the same issue was addressed for aggrid.

[falkoschindler]

Thanks, @zilch42, that's a good thought. The difference between ui.aggrid and ui.table is, in my opinion, that ui.aggrid provides its own method for loading a dataframe. In your case you're extracting rows and columns yourself, so ui.table assumes they are normal JSON-serializable lists of dictionaries. Inspecting rows and columns to catch such invalid datatypes could be rather costly and usually not necessary.

Maybe ui.table should provide a from_pandas method as well? It should be very similar to the one in ui.table and the user wouldn't need to deal with the conversion anymore. Would you like to create a pull request? 🙂

[zilch42]

Thanks @falkoschindler . I'm happy to have a go at it

[falkoschindler]

Great, PR #1983 is merged into main and will be part of the next release.

[zilch42]

Thanks!