pandas-dev/pandas · error · TypeError

cannot subtract {type(self).__name__} from {type(other).__na

Error message

cannot subtract {type(self).__name__} from {type(other).__name__}[{other.dtype}]

What it means

Raised by __rsub__ when self.dtype.kind == 'M' (DatetimeArray) and the left operand other has a dtype but is not itself datelike. Reflected subtraction (other - DatetimeArray) is only defined for datelike left operands; anything else (numeric, object) is rejected with a message that includes other's dtype.

Source

Thrown at pandas/core/arrays/datetimelike.py:1452

            other_dtype, DatetimeTZDtype
        )

        if other_is_dt64 and lib.is_np_dtype(self.dtype, "m"):
            # ndarray[datetime64] cannot be subtracted from self, so
            # we need to wrap in DatetimeArray/Index and flip the operation
            if lib.is_scalar(other):
                # i.e. np.datetime64 object
                return Timestamp(other) - self
            if not isinstance(other, DatetimeLikeArrayMixin):
                # Avoid down-casting DatetimeIndex
                from pandas.core.arrays import DatetimeArray

                other = DatetimeArray._from_sequence(other, dtype=other.dtype)
            return other - self
        elif self.dtype.kind == "M" and hasattr(other, "dtype") and not other_is_dt64:
            # GH#19959 datetime - datetime is well-defined as timedelta,
            # but any other type - datetime is not well-defined.
            raise TypeError(
                f"cannot subtract {type(self).__name__} from "
                f"{type(other).__name__}[{other.dtype}]"
            )
        elif isinstance(self.dtype, PeriodDtype) and lib.is_np_dtype(other_dtype, "m"):
            # TODO: Can we simplify/generalize these cases at all?
            raise TypeError(f"cannot subtract {type(self).__name__} from {other.dtype}")
        elif lib.is_np_dtype(self.dtype, "m"):
            self = cast("TimedeltaArray", self)
            return (-self) + other

        flipped = self - other
        if flipped.dtype.kind == "M":
            # GH#59571 give a more helpful exception message
            raise TypeError(
                f"cannot subtract {type(self).__name__} from {type(other).__name__}"
            )
        # We get here with e.g. datetime objects
        return -flipped

View on GitHub (pinned to 71959b8cb9)

Solutions

1. Reorder the expression so the DatetimeArray is on the left, or convert the left operand to a Timestamp.
2. Cast the numeric operand to a timedelta if a duration was intended: pd.Timedelta(...) - datetime_idx is still invalid — flip to datetime_idx - pd.Timedelta(...).
3. Convert the DatetimeArray to int64 ordinals before numeric subtraction: datetime_idx.astype('int64').
4. Validate the left operand's dtype is datetime-like before reflected subtraction.

Example fix

// before
out = 0 - datetime_idx  # TypeError: cannot subtract DatetimeArray from ndarray[int64]
// after
out = datetime_idx - datetime_idx[0]  # yields TimedeltaIndex

from pandas.api.types import is_datetime64_any_dtype
if not (isinstance(other, (pd.Timestamp, pd.DatetimeIndex)) or is_datetime64_any_dtype(getattr(other, 'dtype', None))):
    raise TypeError('left operand must be datelike for reflected subtraction from DatetimeArray')

def valid_rsub_left(other) -> bool:
    from pandas.api.types import is_datetime64_any_dtype
    return isinstance(other, (pd.Timestamp, pd.DatetimeIndex)) or is_datetime64_any_dtype(getattr(other, 'dtype', None))

try:
    out = other - datetime_idx
except TypeError as e:
    if 'cannot subtract' in str(e):
        out = datetime_idx - other  # flip to direct op
    else:
        raise

When it happens

Trigger: np.array([1,2,3]) - datetime_idx, or int_series - DatetimeIndex, dispatched to __rsub__ at line 1431; the branch at line 1449 fires because other_is_dt64 is False.

Common situations: Reversed arithmetic in expressions like 0 - df['timestamp']; numpy broadcasting a scalar across a DatetimeIndex; mis-typed join keys.

Related errors

• cannot subtract a datelike from a {type(self).__name__}
• cannot subtract {type(self).__name__} from {type(other).__na
• cannot subtract {type(self).__name__} from {other.dtype}
• [datetimelike_compat=True] {left._values} is not equal to {r
• overflow in timedelta operation

AI-assisted analysis of pandas-dev/pandas@71959b8cb9 (2026-08-07). Data as JSON: /api/errors/421af7c50f81d520. Report an issue: GitHub.