BUG: Cleanup timedelta offset

Author: sinhrks

doc/source/whatsnew/v0.24.0.txt

@@ -1126,6 +1126,8 @@ Timedelta
 - Fixed bug in adding a :class:`DataFrame` with all-`timedelta64[ns]` dtypes to a :class:`DataFrame` with all-integer dtypes returning incorrect results instead of raising ``TypeError`` (:issue:`22696`)
 - Bug in :class:`TimedeltaIndex` where adding a timezone-aware datetime scalar incorrectly returned a timezone-naive :class:`DatetimeIndex` (:issue:`23215`)
 - Bug in :class:`TimedeltaIndex` where adding ``np.timedelta64('NaT')`` incorrectly returned an all-`NaT` :class:`DatetimeIndex` instead of an all-`NaT` :class:`TimedeltaIndex` (:issue:`23215`)
+- Bug in :class:`Timedelta` and :func:`to_timedelta()` have inconsistencies in supported unit string (:issue:`21762`)
+
 
 Timezones
 ^^^^^^^^^

pandas/_libs/tslibs/timedeltas.pxd

@@ -6,3 +6,6 @@ from numpy cimport int64_t
 cdef int64_t cast_from_unit(object ts, object unit) except? -1
 cpdef int64_t delta_to_nanoseconds(delta) except? -1
 cpdef convert_to_timedelta64(object ts, object unit)
+
+# Exposed for Timedelta, not intended for outside use.
+cpdef object parse_timedelta_unit(object unit)

pandas/_libs/tslibs/timedeltas.pyx

@@ -44,10 +44,16 @@ Components = collections.namedtuple('Components', [
     'days', 'hours', 'minutes', 'seconds',
     'milliseconds', 'microseconds', 'nanoseconds'])
 
-cdef dict timedelta_abbrevs = { 'D': 'd',
-                                'd': 'd',
-                                'days': 'd',
-                                'day': 'd',
+
+cdef dict timedelta_abbrevs = { 'Y': 'Y',
+                                'y': 'Y',
+                                'M': 'M',
+                                'W': 'W',
+                                'w': 'W',
+                                'D': 'D',
+                                'd': 'D',
+                                'days': 'D',
+                                'day': 'D',
                                 'hours': 'h',
                                 'hour': 'h',
                                 'hr': 'h',
@@ -56,6 +62,7 @@ cdef dict timedelta_abbrevs = { 'D': 'd',
                                 'minute': 'm',
                                 'min': 'm',
                                 'minutes': 'm',
+                                't': 'm',
                                 's': 's',
                                 'seconds': 's',
                                 'sec': 's',
@@ -65,16 +72,19 @@ cdef dict timedelta_abbrevs = { 'D': 'd',
                                 'millisecond': 'ms',
                                 'milli': 'ms',
                                 'millis': 'ms',
+                                'l': 'ms',
                                 'us': 'us',
                                 'microseconds': 'us',
                                 'microsecond': 'us',
                                 'micro': 'us',
                                 'micros': 'us',
+                                'u': 'us',
                                 'ns': 'ns',
                                 'nanoseconds': 'ns',
                                 'nano': 'ns',
                                 'nanos': 'ns',
-                                'nanosecond': 'ns'}
+                                'nanosecond': 'ns',
+                                'n': 'ns'}
 
 _no_input = object()
 
@@ -137,7 +147,8 @@ cpdef int64_t delta_to_nanoseconds(delta) except? -1:
 
 cpdef convert_to_timedelta64(object ts, object unit):
     """
-    Convert an incoming object to a timedelta64 if possible
+    Convert an incoming object to a timedelta64 if possible.
+    Before calling, unit must be standardized to avoid repeated unit conversion
 
     Handle these types of objects:
         - timedelta/Timedelta
@@ -223,6 +234,7 @@ def array_to_timedelta64(object[:] values, unit='ns', errors='raise'):
         for i in range(n):
             result[i] = parse_timedelta_string(values[i])
     except:
+        unit = parse_timedelta_unit(unit)
         for i in range(n):
             try:
                 result[i] = convert_to_timedelta64(values[i], unit)
@@ -242,7 +254,16 @@ cdef inline int64_t cast_from_unit(object ts, object unit) except? -1:
         int64_t m
         int p
 
-    if unit == 'D' or unit == 'd':
+    if unit == 'Y':
+        m = 1000000000L * 31556952
+        p = 9
+    elif unit == 'M':
+        m = 1000000000L * 2629746
+        p = 9
+    elif unit == 'W':
+        m = 1000000000L * 86400 * 7
+        p = 9
+    elif unit == 'D' or unit == 'd':
         m = 1000000000L * 86400
         p = 9
     elif unit == 'h':
@@ -480,14 +501,34 @@ cdef inline timedelta_from_spec(object number, object frac, object unit):
 
     try:
         unit = ''.join(unit)
-        unit = timedelta_abbrevs[unit.lower()]
+        if unit == 'M':
+            # To parse ISO 8601 string, 'M' should be treated as minute,
+            # not month
+            unit = 'm'
+        unit = parse_timedelta_unit(unit)
     except KeyError:
         raise ValueError("invalid abbreviation: {unit}".format(unit=unit))
 
     n = ''.join(number) + '.' + ''.join(frac)
     return cast_from_unit(float(n), unit)
 
 
+cpdef inline object parse_timedelta_unit(object unit):
+    """
+    Parameters
+    ----------
+    unit : an unit string
+    """
+    if unit is None:
+        return 'ns'
+    elif unit == 'M':
+        return unit
+    try:
+        return timedelta_abbrevs[unit.lower()]
+    except (KeyError, AttributeError):
+        raise ValueError("invalid unit abbreviation: {unit}"
+                         .format(unit=unit))
+
 # ----------------------------------------------------------------------
 # Timedelta ops utilities
 
@@ -1065,7 +1106,13 @@ class Timedelta(_Timedelta):
     Parameters
     ----------
     value : Timedelta, timedelta, np.timedelta64, string, or integer
-    unit : string, {'ns', 'us', 'ms', 's', 'm', 'h', 'D'}, optional
+    unit : string, {'Y', 'M', 'W', 'D', 'days', 'day',
+                    'hours', hour', 'hr', 'h', 'm', 'minute', 'min', 'minutes',
+                    'T', 'S', 'seconds', 'sec', 'second', 'ms',
+                    'milliseconds', 'millisecond', 'milli', 'millis', 'L',
+                    'us', 'microseconds', 'microsecond', 'micro', 'micros',
+                    'U', 'ns', 'nanoseconds', 'nano', 'nanos', 'nanosecond'
+                    'N'}, optional
         Denote the unit of the input, if input is an integer. Default 'ns'.
     days, seconds, microseconds,
     milliseconds, minutes, hours, weeks : numeric, optional
@@ -1116,6 +1163,7 @@ class Timedelta(_Timedelta):
             value = np.timedelta64(delta_to_nanoseconds(value.delta), 'ns')
         elif is_integer_object(value) or is_float_object(value):
             # unit=None is de-facto 'ns'
+            unit = parse_timedelta_unit(unit)
             value = convert_to_timedelta64(value, unit)
         elif checknull_with_nat(value):
             return NaT

pandas/core/tools/timedeltas.py

@@ -6,7 +6,8 @@
 import pandas as pd
 from pandas._libs import tslibs
 from pandas._libs.tslibs.timedeltas import (convert_to_timedelta64,
-                                            array_to_timedelta64)
+                                            array_to_timedelta64,
+                                            parse_timedelta_unit)
 
 from pandas.core.dtypes.common import (
     ensure_object,
@@ -23,8 +24,14 @@ def to_timedelta(arg, unit='ns', box=True, errors='raise'):
     Parameters
     ----------
     arg : string, timedelta, list, tuple, 1-d array, or Series
-    unit : unit of the arg (D,h,m,s,ms,us,ns) denote the unit, which is an
-        integer/float number
+    unit : string, {'Y', 'M', 'W', 'D', 'days', 'day',
+                    'hours', hour', 'hr', 'h', 'm', 'minute', 'min', 'minutes',
+                    'T', 'S', 'seconds', 'sec', 'second', 'ms',
+                    'milliseconds', 'millisecond', 'milli', 'millis', 'L',
+                    'us', 'microseconds', 'microsecond', 'micro', 'micros',
+                    'U', 'ns', 'nanoseconds', 'nano', 'nanos', 'nanosecond'
+                    'N'}, optional
+        Denote the unit of the input, if input is an integer. Default 'ns'.
     box : boolean, default True
         - If True returns a Timedelta/TimedeltaIndex of the results
         - if False returns a np.timedelta64 or ndarray of values of dtype
@@ -69,7 +76,7 @@ def to_timedelta(arg, unit='ns', box=True, errors='raise'):
     pandas.DataFrame.astype : Cast argument to a specified dtype.
     pandas.to_datetime : Convert argument to datetime.
     """
-    unit = _validate_timedelta_unit(unit)
+    unit = parse_timedelta_unit(unit)
 
     if errors not in ('ignore', 'raise', 'coerce'):
         raise ValueError("errors must be one of 'ignore', "
@@ -99,45 +106,6 @@ def to_timedelta(arg, unit='ns', box=True, errors='raise'):
                                             box=box, errors=errors)
 
 
-_unit_map = {
-    'Y': 'Y',
-    'y': 'Y',
-    'W': 'W',
-    'w': 'W',
-    'D': 'D',
-    'd': 'D',
-    'days': 'D',
-    'Days': 'D',
-    'day': 'D',
-    'Day': 'D',
-    'M': 'M',
-    'H': 'h',
-    'h': 'h',
-    'm': 'm',
-    'T': 'm',
-    'S': 's',
-    's': 's',
-    'L': 'ms',
-    'MS': 'ms',
-    'ms': 'ms',
-    'US': 'us',
-    'us': 'us',
-    'NS': 'ns',
-    'ns': 'ns',
-}
-
-
-def _validate_timedelta_unit(arg):
-    """ provide validation / translation for timedelta short units """
-    try:
-        return _unit_map[arg]
-    except (KeyError, TypeError):
-        if arg is None:
-            return 'ns'
-        raise ValueError("invalid timedelta unit {arg} provided"
-                         .format(arg=arg))
-
-
 def _coerce_scalar_to_timedelta_type(r, unit='ns', box=True, errors='raise'):
     """Convert string 'r' to a timedelta object."""
 

pandas/tests/scalar/timedelta/test_timedelta.py

@@ -293,37 +293,65 @@ def test_nat_converters(self):
         assert to_timedelta('nat', box=False).astype('int64') == iNaT
         assert to_timedelta('nan', box=False).astype('int64') == iNaT
 
-        def testit(unit, transform):
-
-            # array
-            result = to_timedelta(np.arange(5), unit=unit)
-            expected = TimedeltaIndex([np.timedelta64(i, transform(unit))
+    @pytest.mark.parametrize('units, np_unit',
+                             [(['Y', 'y'], 'Y'),
+                              (['M'], 'M'),
+                              (['W', 'w'], 'W'),
+                              (['D', 'd', 'days', 'day', 'Days', 'Day'], 'D'),
+                              (['m', 'minute', 'min', 'minutes', 't',
+                                'Minute', 'Min', 'Minutes', 'T'], 'm'),
+                              (['s', 'seconds', 'sec', 'second',
+                                'S', 'Seconds', 'Sec', 'Second'], 's'),
+                              (['ms', 'milliseconds', 'millisecond', 'milli',
+                                'millis', 'l', 'MS', 'Milliseconds',
+                                'Millisecond', 'Milli', 'Millis', 'L'], 'ms'),
+                              (['us', 'microseconds', 'microsecond', 'micro',
+                                'micros', 'u', 'US', 'Microseconds',
+                                'Microsecond', 'Micro', 'Micros', 'U'], 'us'),
+                              (['ns', 'nanoseconds', 'nanosecond', 'nano',
+                                'nanos', 'n', 'NS', 'Nanoseconds',
+                                'Nanosecond', 'Nano', 'Nanos', 'N'], 'ns')])
+    def test_unit_parser(self, units, np_unit):
+        # validate all units, GH 6855, GH 21762
+        for unit in units:
+            # array-likes
+            expected = TimedeltaIndex([np.timedelta64(i, np_unit)
                                        for i in np.arange(5).tolist()])
-            tm.assert_index_equal(result, expected)
+            for wrapper in [np.array, list, pd.Index]:
+                result = to_timedelta(wrapper(range(5)), unit=unit)
+                tm.assert_index_equal(result, expected)
+                result = TimedeltaIndex(wrapper(range(5)), unit=unit)
+                tm.assert_index_equal(result, expected)
+
+            if unit == 'M':
+                # M is treated as minutes in string repr
+                expected = TimedeltaIndex([np.timedelta64(i, 'm')
+                                           for i in np.arange(5).tolist()])
+
+            for wrapper in [np.array, list, pd.Index]:
+                str_repr = ['{}{}'.format(x, unit) for x in np.arange(5)]
+                result = to_timedelta(wrapper(str_repr))
+                tm.assert_index_equal(result, expected)
+                result = TimedeltaIndex(wrapper(str_repr))
+                tm.assert_index_equal(result, expected)
 
             # scalar
-            result = to_timedelta(2, unit=unit)
-            expected = Timedelta(np.timedelta64(2, transform(unit)).astype(
+            expected = Timedelta(np.timedelta64(2, np_unit).astype(
                 'timedelta64[ns]'))
-            assert result == expected
 
-        # validate all units
-        # GH 6855
-        for unit in ['Y', 'M', 'W', 'D', 'y', 'w', 'd']:
-            testit(unit, lambda x: x.upper())
-        for unit in ['days', 'day', 'Day', 'Days']:
-            testit(unit, lambda x: 'D')
-        for unit in ['h', 'm', 's', 'ms', 'us', 'ns', 'H', 'S', 'MS', 'US',
-                     'NS']:
-            testit(unit, lambda x: x.lower())
-
-        # offsets
+            result = to_timedelta(2, unit=unit)
+            assert result == expected
+            result = Timedelta(2, unit=unit)
+            assert result == expected
 
-        # m
-        testit('T', lambda x: 'm')
+            if unit == 'M':
+                expected = Timedelta(np.timedelta64(2, 'm').astype(
+                    'timedelta64[ns]'))
 
-        # ms
-        testit('L', lambda x: 'ms')
+            result = to_timedelta('2{}'.format(unit))
+            assert result == expected
+            result = Timedelta('2{}'.format(unit))
+            assert result == expected
 
     def test_numeric_conversions(self):
         assert ct(0) == np.timedelta64(0, 'ns')