DEPR: is_all_dates (#36697)

Author: jbrockmendel

doc/source/whatsnew/v1.2.0.rst

@@ -214,6 +214,8 @@ Deprecations
 - :meth:`DataFrame.lookup` is deprecated and will be removed in a future version, use :meth:`DataFrame.melt` and :meth:`DataFrame.loc` instead (:issue:`18682`)
 - The :meth:`Index.to_native_types` is deprecated. Use ``.astype(str)`` instead (:issue:`28867`)
 - Deprecated indexing :class:`DataFrame` rows with datetime-like strings ``df[string]``, use ``df.loc[string]`` instead (:issue:`36179`)
+- Deprecated casting an object-dtype index of ``datetime`` objects to :class:`DatetimeIndex` in the :class:`Series` constructor (:issue:`23598`)
+- Deprecated :meth:`Index.is_all_dates` (:issue:`27744`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/generic.py

@@ -9528,7 +9528,13 @@ def truncate(
 
         # if we have a date index, convert to dates, otherwise
         # treat like a slice
-        if ax.is_all_dates:
+        if ax._is_all_dates:
+            if is_object_dtype(ax.dtype):
+                warnings.warn(
+                    "Treating object-dtype Index of date objects as DatetimeIndex "
+                    "is deprecated, will be removed in a future version.",
+                    FutureWarning,
+                )
             from pandas.core.tools.datetimes import to_datetime
 
             before = to_datetime(before)

pandas/core/indexes/base.py

@@ -2086,12 +2086,25 @@ def inferred_type(self) -> str_t:
         return lib.infer_dtype(self._values, skipna=False)
 
     @cache_readonly
-    def is_all_dates(self) -> bool:
+    def _is_all_dates(self) -> bool:
         """
         Whether or not the index values only consist of dates.
         """
         return is_datetime_array(ensure_object(self._values))
 
+    @cache_readonly
+    def is_all_dates(self):
+        """
+        Whether or not the index values only consist of dates.
+        """
+        warnings.warn(
+            "Index.is_all_dates is deprecated, will be removed in a future version.  "
+            "check index.inferred_type instead",
+            FutureWarning,
+            stacklevel=2,
+        )
+        return self._is_all_dates
+
     # --------------------------------------------------------------------
     # Pickle Methods
 

pandas/core/indexes/datetimelike.py

@@ -98,7 +98,7 @@ class DatetimeIndexOpsMixin(ExtensionIndex):
     _hasnans = hasnans  # for index / array -agnostic code
 
     @property
-    def is_all_dates(self) -> bool:
+    def _is_all_dates(self) -> bool:
         return True
 
     # ------------------------------------------------------------------------

pandas/core/indexes/interval.py

@@ -1092,7 +1092,7 @@ def func(self, other, sort=sort):
     # --------------------------------------------------------------------
 
     @property
-    def is_all_dates(self) -> bool:
+    def _is_all_dates(self) -> bool:
         """
         This is False even when left/right contain datetime-like objects,
         as the check is done on the Interval itself

pandas/core/indexes/multi.py

@@ -1733,7 +1733,7 @@ def to_flat_index(self):
         return Index(self._values, tupleize_cols=False)
 
     @property
-    def is_all_dates(self) -> bool:
+    def _is_all_dates(self) -> bool:
         return False
 
     def is_lexsorted(self) -> bool:

pandas/core/indexes/numeric.py

@@ -149,7 +149,7 @@ def _assert_safe_casting(cls, data, subarr):
         pass
 
     @property
-    def is_all_dates(self) -> bool:
+    def _is_all_dates(self) -> bool:
         """
         Checks that all the labels are datetime objects.
         """

pandas/core/missing.py

@@ -199,7 +199,7 @@ def interpolate_1d(
         return yvalues
 
     if method == "time":
-        if not getattr(xvalues, "is_all_dates", None):
+        if not getattr(xvalues, "_is_all_dates", None):
             # if not issubclass(xvalues.dtype.type, np.datetime64):
             raise ValueError(
                 "time-weighted interpolation only works "
@@ -327,7 +327,7 @@ def _interpolate_scipy_wrapper(
         "piecewise_polynomial": _from_derivatives,
     }
 
-    if getattr(x, "is_all_dates", False):
+    if getattr(x, "_is_all_dates", False):
         # GH 5975, scipy.interp1d can't handle datetime64s
         x, new_x = x._values.astype("i8"), new_x.astype("i8")
 

pandas/core/series.py

@@ -409,14 +409,20 @@ def _set_axis(self, axis: int, labels, fastpath: bool = False) -> None:
         if not fastpath:
             labels = ensure_index(labels)
 
-        is_all_dates = labels.is_all_dates
-        if is_all_dates:
+        if labels._is_all_dates:
             if not isinstance(labels, (DatetimeIndex, PeriodIndex, TimedeltaIndex)):
                 try:
                     labels = DatetimeIndex(labels)
                     # need to set here because we changed the index
                     if fastpath:
                         self._mgr.set_axis(axis, labels)
+                    warnings.warn(
+                        "Automatically casting object-dtype Index of datetimes to "
+                        "DatetimeIndex is deprecated and will be removed in a "
+                        "future version.  Explicitly cast to DatetimeIndex instead.",
+                        FutureWarning,
+                        stacklevel=3,
+                    )
                 except (tslibs.OutOfBoundsDatetime, ValueError):
                     # labels may exceeds datetime bounds,
                     # or not be a DatetimeIndex

pandas/plotting/_matplotlib/core.py

@@ -1238,7 +1238,7 @@ def get_label(i):
         # would be too close together.
         condition = (
             not self._use_dynamic_x()
-            and (data.index.is_all_dates and self.use_index)
+            and (data.index._is_all_dates and self.use_index)
             and (not self.subplots or (self.subplots and self.sharex))
         )