ENH: add to_offset method to Timedelta #9064

doc/source/whatsnew/v0.16.0.txt

@@ -99,6 +99,7 @@ Enhancements
 - Added time interval selection in get_data_yahoo (:issue:`9071`)
 - Added ``Series.str.slice_replace()``, which previously raised NotImplementedError (:issue:`8888`)
 - Added ``Timestamp.to_datetime64()`` to complement ``Timedelta.to_timedelta64()`` (:issue:`9255`)
+- ``tseries.frequencies.to_offset()`` now accepts ``Timedelta`` as input (:issue:`9064`)
 
 
 Performance

pandas/tseries/frequencies.py

@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import datetime,timedelta
 from pandas.compat import range, long, zip
 from pandas import compat
 import re
@@ -12,6 +12,7 @@
 import pandas.core.common as com
 import pandas.lib as lib
 import pandas.tslib as tslib
+from pandas.tslib import Timedelta
 
 class FreqGroup(object):
     FR_ANN = 1000
@@ -276,9 +277,18 @@ def get_period_alias(offset_str):
 _legacy_reverse_map = dict((v, k) for k, v in
                            reversed(sorted(compat.iteritems(_rule_aliases))))
 
+_name_to_offset_map = {'days': Day(1),
+                       'hours': Hour(1),
+                       'minutes': Minute(1),
+                       'seconds': Second(1),
+                       'milliseconds': Milli(1),
+                       'microseconds': Micro(1),
+                       'nanoseconds': Nano(1)}
+
 def to_offset(freqstr):
     """
-    Return DateOffset object from string representation
+    Return DateOffset object from string representation or
+    Timedelta object
 
     Examples
     --------
@@ -298,6 +308,23 @@ def to_offset(freqstr):
             name, stride = stride, name
         name, _ = _base_and_stride(name)
         delta = get_offset(name) * stride
+
+    elif isinstance(freqstr, timedelta):
+        delta = None
+        freqstr = Timedelta(freqstr)
+        try:
+            for name in freqstr.components._fields:
+                offset = _name_to_offset_map[name]
+                stride = getattr(freqstr.components, name)
+                if stride != 0:
+                    offset = stride * offset
+                    if delta is None:
+                        delta = offset
+                    else:
+                        delta = delta + offset
+        except Exception:
+            raise ValueError("Could not evaluate %s" % freqstr)
+
     else:
         delta = None
         stride_sign = None

pandas/tseries/tests/test_frequencies.py

@@ -17,6 +17,7 @@
 import pandas.compat as compat
 
 import pandas.util.testing as tm
+from pandas import Timedelta
 
 def test_to_offset_multiple():
     freqstr = '2h30min'
@@ -81,6 +82,47 @@ def test_to_offset_leading_zero():
     assert(result.n == -194)
 
 
+def test_to_offset_pd_timedelta():
+    # Tests for #9064
+    td = Timedelta(days=1, seconds=1)
+    result = frequencies.to_offset(td)
+    expected = offsets.Second(86401)
+    assert(expected==result)
+
+    td = Timedelta(days=-1, seconds=1)
+    result = frequencies.to_offset(td)
+    expected = offsets.Second(-86399)
+    assert(expected==result)
+
+    td = Timedelta(hours=1, minutes=10)
+    result = frequencies.to_offset(td)
+    expected = offsets.Minute(70)
+    assert(expected==result)
+
+    td = Timedelta(hours=1, minutes=-10)
+    result = frequencies.to_offset(td)
+    expected = offsets.Minute(50)
+    assert(expected==result)
+
+    td = Timedelta(weeks=1)
+    result = frequencies.to_offset(td)
+    expected = offsets.Day(7)
+    assert(expected==result)
+
+    td1 = Timedelta(hours=1)
+    result1 = frequencies.to_offset(td1)
+    result2 = frequencies.to_offset('60min')
+    assert(result1 == result2)
+
+    td = Timedelta(microseconds=1)
+    result = frequencies.to_offset(td)
+    expected = offsets.Micro(1)
+    assert(expected == result)
+
+    td = Timedelta(microseconds=0)
+    tm.assertRaises(ValueError, lambda: frequencies.to_offset(td))
+
+
 def test_anchored_shortcuts():
     result = frequencies.to_offset('W')
     expected = frequencies.to_offset('W-SUN')