Implement TimedeltaArray._from_sequence (pandas-dev#23953)

Author: jbrockmendel

pandas/core/arrays/timedeltas.py

@@ -163,11 +163,17 @@ def _simple_new(cls, values, freq=None, dtype=_TD_DTYPE):
         return result
 
     def __new__(cls, values, freq=None, dtype=_TD_DTYPE, copy=False):
+        return cls._from_sequence(values, freq=freq, dtype=dtype, copy=copy)
+
+    @classmethod
+    def _from_sequence(cls, data, freq=None, unit=None,
+                       dtype=_TD_DTYPE, copy=False):
+        if dtype != _TD_DTYPE:
+            raise ValueError("Only timedelta64[ns] dtype is valid.")
 
         freq, freq_infer = dtl.maybe_infer_freq(freq)
 
-        values, inferred_freq = sequence_to_td64ns(
-            values, copy=copy, unit=None)
+        data, inferred_freq = sequence_to_td64ns(data, copy=copy, unit=unit)
         if inferred_freq is not None:
             if freq is not None and freq != inferred_freq:
                 raise ValueError('Inferred frequency {inferred} from passed '
@@ -179,13 +185,13 @@ def __new__(cls, values, freq=None, dtype=_TD_DTYPE, copy=False):
                 freq = inferred_freq
             freq_infer = False
 
-        result = cls._simple_new(values, freq=freq)
-        # check that we are matching freqs
-        if inferred_freq is None and len(result) > 0:
-            if freq is not None and not freq_infer:
-                cls._validate_frequency(result, freq)
+        result = cls._simple_new(data, freq=freq)
+
+        if inferred_freq is None and freq is not None:
+            # this condition precludes `freq_infer`
+            cls._validate_frequency(result, freq)
 
-        if freq_infer:
+        elif freq_infer:
             result.freq = to_offset(result.inferred_freq)
 
         return result
@@ -666,7 +672,7 @@ def sequence_to_td64ns(data, copy=False, unit="ns", errors="raise"):
         warnings.warn("Passing datetime64-dtype data to TimedeltaIndex is "
                       "deprecated, will raise a TypeError in a future "
                       "version",
-                      FutureWarning, stacklevel=3)
+                      FutureWarning, stacklevel=4)
         data = ensure_int64(data).view(_TD_DTYPE)
 
     else:

pandas/core/indexes/timedeltas.py

@@ -17,8 +17,7 @@
 
 from pandas.core.arrays import datetimelike as dtl
 from pandas.core.arrays.timedeltas import (
-    TimedeltaArrayMixin as TimedeltaArray, _is_convertible_to_td, _to_m8,
-    sequence_to_td64ns)
+    TimedeltaArrayMixin as TimedeltaArray, _is_convertible_to_td, _to_m8)
 from pandas.core.base import _shared_docs
 import pandas.core.common as com
 from pandas.core.indexes.base import Index, _index_shared_docs
@@ -132,7 +131,7 @@ def _join_i8_wrapper(joinf, **kwargs):
     # Constructors
 
     def __new__(cls, data=None, unit=None, freq=None, start=None, end=None,
-                periods=None, closed=None, dtype=None, copy=False,
+                periods=None, closed=None, dtype=_TD_DTYPE, copy=False,
                 name=None, verify_integrity=None):
 
         if verify_integrity is not None:
@@ -142,9 +141,8 @@ def __new__(cls, data=None, unit=None, freq=None, start=None, end=None,
         else:
             verify_integrity = True
 
-        freq, freq_infer = dtl.maybe_infer_freq(freq)
-
         if data is None:
+            freq, freq_infer = dtl.maybe_infer_freq(freq)
             warnings.warn("Creating a TimedeltaIndex by passing range "
                           "endpoints is deprecated.  Use "
                           "`pandas.timedelta_range` instead.",
@@ -167,29 +165,10 @@ def __new__(cls, data=None, unit=None, freq=None, start=None, end=None,
 
         # - Cases checked above all return/raise before reaching here - #
 
-        data, inferred_freq = sequence_to_td64ns(data, copy=copy, unit=unit)
-        if inferred_freq is not None:
-            if freq is not None and freq != inferred_freq:
-                raise ValueError('Inferred frequency {inferred} from passed '
-                                 'values does not conform to passed frequency '
-                                 '{passed}'
-                                 .format(inferred=inferred_freq,
-                                         passed=freq.freqstr))
-            elif freq_infer:
-                freq = inferred_freq
-                freq_infer = False
-            verify_integrity = False
-
-        subarr = cls._simple_new(data, name=name, freq=freq)
-        # check that we are matching freqs
-        if verify_integrity and len(subarr) > 0:
-            if freq is not None and not freq_infer:
-                cls._validate_frequency(subarr, freq)
-
-        if freq_infer:
-            subarr.freq = to_offset(subarr.inferred_freq)
-
-        return subarr
+        result = cls._from_sequence(data, freq=freq, unit=unit,
+                                    dtype=dtype, copy=copy)
+        result.name = name
+        return result
 
     @classmethod
     def _simple_new(cls, values, name=None, freq=None, dtype=_TD_DTYPE):

pandas/tests/arrays/test_timedeltas.py

@@ -1,13 +1,20 @@
 # -*- coding: utf-8 -*-
 
 import numpy as np
+import pytest
 
 import pandas as pd
 from pandas.core.arrays import TimedeltaArrayMixin as TimedeltaArray
 import pandas.util.testing as tm
 
 
 class TestTimedeltaArray(object):
+    def test_from_sequence_dtype(self):
+        msg = r"Only timedelta64\[ns\] dtype is valid"
+        with pytest.raises(ValueError, match=msg):
+            TimedeltaArray._from_sequence([], dtype=object)
+        with pytest.raises(ValueError, match=msg):
+            TimedeltaArray([], dtype=object)
 
     def test_abs(self):
         vals = np.array([-3600 * 10**9, 'NaT', 7200 * 10**9], dtype='m8[ns]')

pandas/tests/dtypes/test_inference.py

@@ -1163,7 +1163,7 @@ def test_is_timedelta(self):
         assert not is_timedelta64_ns_dtype('timedelta64')
         assert is_timedelta64_ns_dtype('timedelta64[ns]')
 
-        tdi = TimedeltaIndex([1e14, 2e14], dtype='timedelta64')
+        tdi = TimedeltaIndex([1e14, 2e14], dtype='timedelta64[ns]')
         assert is_timedelta64_dtype(tdi)
         assert is_timedelta64_ns_dtype(tdi)
         assert is_timedelta64_ns_dtype(tdi.astype('timedelta64[ns]'))