BUG: Bug in to_timedelta that accepted invalid units and misinterpreted m/h (GH7611, GH6423)

doc/source/v0.14.1.txt

@@ -176,7 +176,7 @@ Bug Fixes
 - Bug in groupby ``.nth`` with a Series and integer-like column name (:issue:`7559`)
 
 - Bug in ``value_counts`` where ``NaT`` did not qualify as missing (``NaN``) (:issue:`7423`)
-
+- Bug in ``to_timedelta`` that accepted invalid units and misinterpreted 'm/h' (:issue:`7611`, :issue: `6423`)
 
 
 - Bug in ``Panel.apply`` with a multi-index as an axis (:issue:`7469`)

pandas/tseries/tests/test_timedeltas.py

@@ -199,20 +199,40 @@ def conv(v):
         expected = Series([ np.timedelta64(1,'D') ]*5)
         tm.assert_series_equal(result, expected)
 
+        def testit(unit, transform):
+
+            # array
+            result = to_timedelta(np.arange(5),unit=unit)
+            expected = Series([ np.timedelta64(i,transform(unit)) for i in np.arange(5).tolist() ])
+            tm.assert_series_equal(result, expected)
+
+            # scalar
+            result = to_timedelta(2,unit=unit)
+            expected = np.timedelta64(2,transform(unit)).astype('timedelta64[ns]')
+            self.assert_numpy_array_equal(result,expected)
+
         # validate all units
         # GH 6855
         for unit in ['Y','M','W','D','y','w','d']:
-            result = to_timedelta(np.arange(5),unit=unit)
-            expected = Series([ np.timedelta64(i,unit.upper()) for i in np.arange(5).tolist() ])
-            tm.assert_series_equal(result, expected)
+            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']:
-            result = to_timedelta(np.arange(5),unit=unit)
-            expected = Series([ np.timedelta64(i,unit.lower()) for i in np.arange(5).tolist() ])
-            tm.assert_series_equal(result, expected)
+            testit(unit,lambda x: x.lower())
+
+        # offsets
+
+        # m
+        testit('T',lambda x: 'm')
+
+        # ms
+        testit('L',lambda x: 'ms')
 
         # these will error
         self.assertRaises(ValueError, lambda : to_timedelta(['1h']))
         self.assertRaises(ValueError, lambda : to_timedelta(['1m']))
+        self.assertRaises(ValueError, lambda : to_timedelta([1,2],unit='foo'))
+        self.assertRaises(ValueError, lambda : to_timedelta(1,unit='foo'))
 
     def test_to_timedelta_via_apply(self):
         _skip_if_numpy_not_friendly()

pandas/tseries/timedeltas.py

@@ -32,6 +32,8 @@ def to_timedelta(arg, box=True, unit='ns'):
     if _np_version_under1p7:
         raise ValueError("to_timedelta is not support for numpy < 1.7")
 
+    unit = _validate_timedelta_unit(unit)
+
     def _convert_listlike(arg, box, unit):
 
         if isinstance(arg, (list,tuple)):
@@ -40,7 +42,6 @@ def _convert_listlike(arg, box, unit):
         if is_timedelta64_dtype(arg):
             value = arg.astype('timedelta64[ns]')
         elif is_integer_dtype(arg):
-            unit = _validate_timedelta_unit(unit)
 
             # these are shortcutable
             value = arg.astype('timedelta64[{0}]'.format(unit)).astype('timedelta64[ns]')
@@ -67,14 +68,39 @@ def _convert_listlike(arg, box, unit):
     # ...so it must be a scalar value. Return scalar.
     return _coerce_scalar_to_timedelta_type(arg, unit=unit)
 
+_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 """
-
-    if re.search("Y|W|D",arg,re.IGNORECASE) or arg == 'M':
-        return arg.upper()
-    elif re.search("h|m|s|ms|us|ns",arg,re.IGNORECASE):
-        return arg.lower()
-    raise ValueError("invalid timedelta unit {0} provided".format(arg))
+    try:
+        return _unit_map[arg]
+    except:
+        raise ValueError("invalid timedelta unit {0} provided".format(arg))
 
 _short_search = re.compile(
     "^\s*(?P<neg>-?)\s*(?P<value>\d*\.?\d*)\s*(?P<unit>d|s|ms|us|ns)?\s*$",re.IGNORECASE)

pandas/tslib.pyx

@@ -1387,11 +1387,17 @@ cdef inline convert_to_timedelta64(object ts, object unit, object coerce):
         else:
             if util.is_array(ts):
                 ts = ts.astype('int64').item()
-            ts = cast_from_unit(ts, unit)
-            if _np_version_under1p7:
-                ts = timedelta(microseconds=ts/1000.0)
+            if unit in ['Y','M','W']:
+                if _np_version_under1p7:
+                    raise ValueError("unsupported unit for native timedelta under this numpy {0}".format(unit))
+                else:
+                    ts = np.timedelta64(ts,unit)
             else:
-                ts = np.timedelta64(ts)
+                ts = cast_from_unit(ts, unit)
+                if _np_version_under1p7:
+                    ts = timedelta(microseconds=ts/1000.0)
+                else:
+                    ts = np.timedelta64(ts)
     elif util.is_string_object(ts):
         if ts in _nat_strings or coerce:
             return np.timedelta64(iNaT)
@@ -1747,6 +1753,12 @@ cpdef inline int64_t cast_from_unit(object ts, object unit) except -1:
     if unit == 'D' or unit == 'd':
         m = 1000000000L * 86400
         p = 6
+    elif unit == 'h':
+        m = 1000000000L * 3600
+        p = 6
+    elif unit == 'm':
+        m = 1000000000L * 60
+        p = 6
     elif unit == 's':
         m = 1000000000L
         p = 6
@@ -1756,9 +1768,11 @@ cpdef inline int64_t cast_from_unit(object ts, object unit) except -1:
     elif unit == 'us':
         m = 1000L
         p = 0
-    else:
+    elif unit == 'ns' or unit is None:
         m = 1L
         p = 0
+    else:
+        raise ValueError("cannot cast unit {0}".format(unit))
 
     # just give me the unit back
     if ts is None: