BUG: `infer_freq` throws exception on `Series` of timezone-aware `Timestamp`s · Issue #52456 · pandas-dev/pandas (original) (raw)

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Reproducible Example

import pandas as pd

index = pd.date_range('2023-01-01', '2023-01-03', tz='America/Los_Angeles') series = index.to_series().reset_index(drop=True) object_series = series.astype(object)

for data in [index, series, object_series]: print('type:', type(data)) print('dtype:', data.dtype) try: freq = pd.infer_freq(data) print('success, freq is', freq) except Exception as e: print(str(e))

Issue Description

When given a Series of timezone-aware Timestamps, infer_freq throws an exception. However, if given a DatetimeIndex of the exact same sequence of timezone-aware Timestamps, it works just fine. The problem comes from that DatetimeTZDtype is not allowed when checking the dtype of the Series. Adding is_datetime64tz_dtype to the dtype check should fix this issue.

if not (
is_datetime64_dtype(values)
or is_timedelta64_dtype(values)
or values.dtype == object
):
raise TypeError(
"cannot infer freq from a non-convertible dtype "
f"on a Series of {index.dtype}"
)

Note that, although the documentation says the input type must be DatetimeIndex or TimedeltaIndex, the type annotation does include Series. The discrepancy among documentation, type annotation, and implementation (which accepts Series and converts it into DatetimeIndex when possible) should also be fixed.

def infer_freq(
index: DatetimeIndex \| TimedeltaIndex	Series	DatetimeLikeArrayMixin,
) -> str \| None:

Actual output of the example:

type: <class 'pandas.core.indexes.datetimes.DatetimeIndex'>
dtype: datetime64[ns, America/Los_Angeles]
success, freq is D
type: <class 'pandas.core.series.Series'>
dtype: datetime64[ns, America/Los_Angeles]
cannot infer freq from a non-convertible dtype on a Series of datetime64[ns, America/Los_Angeles]
type: <class 'pandas.core.series.Series'>
dtype: object
success, freq is D

Expected Behavior

infer_freq should accept Series of timezone-aware timestamps, convert it into DateTimeIndex, and proceed as usual.

Installed Versions