FutureWarning: casting datetime64[ns] values to int64 with .astype(...) is deprecated

[hoxbro]

ALL software version info

numpy.__version__ = '1.20.3'
holoviews.__version__ = '1.14.6'

Description of expected behavior and the observed behavior

Casting datetime64[ns] values to int64 with .astype(...) is deprecated

Complete, minimal, self-contained example code that reproduces the issue

import hvplot.pandas  # noqa
import pandas as pd

df = pd.DataFrame({
    "time": pd.date_range("2020", "2021" ,100),
    "data": 100 * [1],
})

df.hvplot.line("time", "data", datashade=True)

Stack traceback and/or browser JavaScript console output

C:\Users\shh\miniconda3\envs\clean_holoviz\lib\site-packages\holoviews\operation\datashader.py:428: FutureWarning: casting datetime64[ns] values to int64 with .astype(...) is deprecated and will raise in a future version. Use .view(...) instead.
  df[d.name] = vals.astype('int64')

[jbednar]

Sounds like a straightforward PR to make from the error message, but then if so I'm not sure why it's deprecated and not simply done automatically any more, so maybe there is more to it than that.

[philippjfr]

Yeah, I don't really understand the reasoning behind this change tbh. We rely on this a lot all over the place iirc.

[hoxbro]

The warning was added here: pandas-dev/pandas#38544

[jbednar]

Oh my; that link leads to a lot of discussion: pandas-dev/pandas#22384 (comment)

I'm not at all sure that the issue has been resolved one way or another, i.e. whether the deprecation will be implemented or reverted, so I'd be inclined to wait on this until such a change is released definitively in pandas.

[hoxbro]

The change will also not be as straightforward as the error message for Holoviews, which also can handle Dask DataFrames and Series, which doesn't have a view attribute. So a function to convert would look something like this:

def convert_to_int64(x):
    if pd.isna(x).any():
        raise ValueError("Cannot convert NaN/NaT values to integer")

    if dd and isinstance(x, (dd.DataFrame, dd.Series)):  # Dask does not have view
        return x.astype("int64")
    else:
        return x.view("int64")

[jbednar]

Ugh! Yes, let's not make this change until we are certain we will need it.

[jorisvandenbossche]

FYI, the deprecation warning has been reverted

[github-actions]

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