BUG: resampling empty dataframe under specific circumstance leads to `Only valid with DatetimeIndex, TimedeltaIndex or PeriodIndex, but got an instance of 'RangeIndex'`

[xytxytxyt]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

import pandas as pd
subdf = pd.DataFrame({'My Column 1': []}, index=pd.to_datetime([], unit='s', utc=True))
df = pd.DataFrame()
df = df.join(subdf, how='outer')
df = df.resample("H").asfreq()

# output:
'''
<stdin>:1: FutureWarning: 'H' is deprecated and will be removed in a future version, please use 'h' instead.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/xytxytxyt/.pyenv/versions/temp/lib/python3.11/site-packages/pandas/core/generic.py", line 9771, in resample
    return get_resampler(
           ^^^^^^^^^^^^^^
  File "/Users/xytxytxyt/.pyenv/versions/temp/lib/python3.11/site-packages/pandas/core/resample.py", line 2050, in get_resampler
    return tg._get_resampler(obj, kind=kind)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/xytxytxyt/.pyenv/versions/temp/lib/python3.11/site-packages/pandas/core/resample.py", line 2272, in _get_resampler
    raise TypeError(
TypeError: Only valid with DatetimeIndex, TimedeltaIndex or PeriodIndex, but got an instance of 'RangeIndex'
'''

Issue Description

see the example

interestingly, this does not happen without the join():

import pandas as pd
df = pd.DataFrame({'My Column 1': []}, index=pd.to_datetime([], unit='s', utc=True))
df = df.resample("H").asfreq()

# output:
# <stdin>:1: FutureWarning: 'H' is deprecated and will be removed in a future version, please use 'h' instead.

Expected Behavior

no error is raised

Installed Versions

INSTALLED VERSIONS

commit : 0691c5c
python : 3.11.8
python-bits : 64
OS : Darwin
OS-release : 22.6.0
Version : Darwin Kernel Version 22.6.0: Mon Apr 22 20:50:39 PDT 2024; root:xnu-8796.141.3.705.2~1/RELEASE_ARM64_T8103
machine : arm64
processor : arm
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.2.3
numpy : 2.1.2
pytz : 2024.2
dateutil : 2.9.0.post0
pip : 24.2
Cython : None
sphinx : None
IPython : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : None
lxml.etree : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : None
pyreadstat : None
pytest : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
tzdata : 2024.2
qtpy : None
pyqt5 : None

[xytxytxyt]

current workaround:

    if len(df.index) > 0:
        df = df.resample("H").asfreq()

[chaoyihu]

The reproducible code is not working. It would be easier if you can provide sample data or show what df looks like after the join.

From the error message, it looks like df.index became RangeIndex after the join and that is why you cannot resample it. I think you should inspect df after the join to make sure df.index is a datetime-like index (DatetimeIndex, PeriodIndex, or TimedeltaIndex).

The workaround seems to suggest that your error only occurs when df is empty. So it might be that your join result is empty for some reason. The index for an empty dataframe is a RangeIndex.

[xytxytxyt]

it's not working in what sense? did it not give an error, or it gave a different error?

there's no sample data because both dataframes are empty

however, if there is only one empty dataframe (with a datetime index), resampling works; but if an empty dataframe with nothing is joined with an empty dataframe with a datetime index, resampling doesn't work

[chaoyihu]

Thanks for clarifying!

it's not working in what sense? did it not give an error, or it gave a different error?
there's no sample data because both dataframes are empty

I see. I thought you omitted the data so I filled it with some timestamps myself. Sorry for the confusion. The code works.

however, if there is only one empty dataframe (with a datetime index), resampling works; but if an empty dataframe with nothing is joined with an empty dataframe with a datetime index, resampling doesn't work

Yes. Because when an empty df with RangeIndex is joined with another empty df with DatetimeIndex, the result dataframe is empty and has RangeIndex. Resampling does not work on a dataframe with RangeIndex. In your code:

>>> df.index
RangeIndex(start=0, stop=0, step=1)
>>> subdf.index
DatetimeIndex([], dtype='datetime64[ns, UTC]', freq=None)
>>> df_joined = df.join(subdf, how='outer')
>>> df_joined.index
RangeIndex(start=0, stop=0, step=1)

However, if you join two empty dataframes that both have DatetimeIndex, the result has DatetimeIndex. The following code should work:

import pandas as pd
subdf = pd.DataFrame({'My Column 1': []}, index=pd.to_datetime([], unit='s', utc=True))
df = pd.DataFrame(index=pd.to_datetime([], unit='s', utc=True))
df = df.join(subdf, how='outer')
df = df.resample("h").asfreq()

Does this answer your question?

[xytxytxyt]

ahh makes sense, thanks for explaining!

will close