COMPAT: infer_freq compat on passing an Index of strings (GH6463)

Author: jreback

doc/source/release.rst

@@ -81,7 +81,8 @@ API Changes
  - ``microsecond,nanosecond,qyear``
  - ``min(),max()``
  - ``pd.infer_freq()``
-- ``pd.infer_freq()`` will now raise a ``TypeError`` if given an invalid ``Series/Index`` type (:issue:`6407`)
+- ``pd.infer_freq()`` will now raise a ``TypeError`` if given an invalid ``Series/Index``
+ type (:issue:`6407`, :issue:`6463`)
 
 - Local variable usage has changed in
  :func:`pandas.eval`/:meth:`DataFrame.eval`/:meth:`DataFrame.query`

pandas/tseries/frequencies.py

@@ -655,8 +655,11 @@ def infer_freq(index, warn=True):
  if isinstance(index, pd.PeriodIndex):
  raise TypeError("PeriodIndex given. Check the `freq` attribute "
  "instead of using infer_freq.")
- if not isinstance(index, pd.DatetimeIndex) and isinstance(index, pd.Index):
- raise TypeError("cannot infer freq from a non-convertible index type {0}".format(type(index)))
+ if isinstance(index, pd.Index) and not isinstance(index, pd.DatetimeIndex):
+ if isinstance(index, (pd.Int64Index, pd.Float64Index)):
+ raise TypeError("cannot infer freq from a non-convertible index type {0}".format(type(index)))
+ index = index.values
+
  index = pd.DatetimeIndex(index)
  inferer = _FrequencyInferer(index, warn=warn)
  return inferer.get_freq()

pandas/tseries/tests/test_frequencies.py

@@ -274,11 +274,20 @@ def test_invalid_index_types(self):
  # test all index types
  for i in [ tm.makeIntIndex(10),
  tm.makeFloatIndex(10),
- tm.makeStringIndex(10),
- tm.makeUnicodeIndex(10),
  tm.makePeriodIndex(10) ]:
  self.assertRaises(TypeError, lambda : infer_freq(i))
 
+ for i in [ tm.makeStringIndex(10),
+ tm.makeUnicodeIndex(10) ]:
+ self.assertRaises(ValueError, lambda : infer_freq(i))
+
+ def test_string_datetimelike_compat(self):
+
+ # GH 6463
+ expected = infer_freq(['2004-01', '2004-02', '2004-03', '2004-04'])
+ result = infer_freq(Index(['2004-01', '2004-02', '2004-03', '2004-04']))
+ self.assertEqual(result,expected)
+
  def test_series(self):
 
  # GH6407