From 0e4e1c2b7f54c1d1bdd7372ac2e1eb6c1df4ce10 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Tue, 12 Feb 2019 23:52:00 +0100
Subject: [PATCH 01/23] Add skipna to pct_change (#25006)

---
 pandas/core/generic.py | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index ef629361c291a..4d40220b62599 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -9948,11 +9948,24 @@ def _check_percentile(self, q):
         """
 
     @Appender(_shared_docs['pct_change'] % _shared_doc_kwargs)
-    def pct_change(self, periods=1, fill_method='pad', limit=None, freq=None,
-                   **kwargs):
+    def pct_change(self, periods=1, fill_method=None, limit=None, freq=None,
+                   skipna=False, **kwargs):
+        if skipna and fill_method is not None:
+            raise ValueError("cannot pass both skipna and fill_method")
+        elif skipna and limit is not None:
+            raise ValueError("cannot pass both skipna and limit")
+        if skipna and self._typ == 'dataframe':
+            return self.apply(
+                lambda s: s.pct_change(periods=periods,
+                                       fill_method=fill_method, limit=limit,
+                                       freq=freq, skipna=skipna, **kwargs)
+            )
         # TODO: Not sure if above is correct - need someone to confirm.
         axis = self._get_axis_number(kwargs.pop('axis', self._stat_axis_name))
-        if fill_method is None:
+        if skipna:
+            # mask = self.isna()
+            data = self.dropna()
+        elif fill_method is None:
             data = self
         else:
             data = self.fillna(method=fill_method, limit=limit, axis=axis)
@@ -9963,6 +9976,8 @@ def pct_change(self, periods=1, fill_method='pad', limit=None, freq=None,
         if freq is None:
             mask = isna(com.values_from_object(data))
             np.putmask(rs.values, mask, np.nan)
+        if skipna:
+            rs = rs.reindex_like(self)
         return rs
 
     def _agg_by_level(self, name, axis=0, level=0, skipna=True, **kwargs):

From 4be1bdca61d049abcf2a099b955c76beb8d834bb Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Tue, 12 Feb 2019 23:52:20 +0100
Subject: [PATCH 02/23] Add tests

---
 pandas/tests/frame/test_analytics.py  | 17 +++++++++++++++++
 pandas/tests/generic/test_generic.py  | 14 ++++++++++++++
 pandas/tests/series/test_analytics.py | 12 ++++++++++++
 3 files changed, 43 insertions(+)

diff --git a/pandas/tests/frame/test_analytics.py b/pandas/tests/frame/test_analytics.py
index 2e690ebbfa121..00d9835090c34 100644
--- a/pandas/tests/frame/test_analytics.py
+++ b/pandas/tests/frame/test_analytics.py
@@ -6,6 +6,7 @@
 import warnings
 
 import numpy as np
+from numpy import nan
 import pytest
 
 from pandas.compat import PY35, lrange
@@ -18,6 +19,7 @@
 import pandas.core.algorithms as algorithms
 import pandas.core.nanops as nanops
 import pandas.util.testing as tm
+from pandas.util.testing import (assert_frame_equal)
 
 
 def assert_stat_op_calc(opname, alternative, frame, has_skipna=True,
@@ -1364,6 +1366,21 @@ def test_pct_change(self):
 
             tm.assert_frame_equal(result, expected)
 
+    @pytest.mark.parametrize("periods, expected_vals", [
+        (1, [[nan, nan], [nan, nan], [1., nan], [0.5, 1.], [nan, 0.5],
+             [0.33333333, nan], [nan, 0.33333333]]),
+        (2, [[nan, nan], [nan, nan], [nan, nan], [ 2., nan], [nan,  2.],
+             [ 1., nan], [nan,  1.]])
+    ])
+    def test_pct_change_skipna(self, periods, expected_vals):
+        # GH25006
+        df = DataFrame([[nan, nan], [ 1., nan], [ 2.,  1.], [ 3.,  2.],
+                        [nan,  3.], [ 4., nan], [nan,  4.]])
+        result = df.pct_change(skipna=True, periods=periods)
+        expected = DataFrame(expected_vals)
+        assert_frame_equal(result, expected)
+
+
     # ----------------------------------------------------------------------
     # Index of max / min
 
diff --git a/pandas/tests/generic/test_generic.py b/pandas/tests/generic/test_generic.py
index fb17b47948336..8b29b4f8dbe39 100644
--- a/pandas/tests/generic/test_generic.py
+++ b/pandas/tests/generic/test_generic.py
@@ -608,6 +608,20 @@ def test_pct_change(self, periods, fill_method, limit, exp):
         else:
             tm.assert_series_equal(res, Series(exp))
 
+    @pytest.mark.xfail(raises=ValueError)
+    @pytest.mark.parametrize('fill_method, limit', [
+        ('backfill', None),
+        ('bfill', None),
+        ('pad', None),
+        ('ffill', None),
+        (None, 1)
+    ])
+    def test_pct_change_skipna_error(self, fill_method, limit):
+        # GH25006
+        vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
+        obj = self._typ(vals)
+        _ = obj.pct_change(skipna=True, fill_method=fill_method, limit=limit)
+        assert True
 
 class TestNDFrame(object):
     # tests that don't fit elsewhere
diff --git a/pandas/tests/series/test_analytics.py b/pandas/tests/series/test_analytics.py
index 6811e370726b2..4f65785412100 100644
--- a/pandas/tests/series/test_analytics.py
+++ b/pandas/tests/series/test_analytics.py
@@ -212,6 +212,18 @@ def test_cummax_timedelta64(self):
         result = s.cummax(skipna=False)
         tm.assert_series_equal(expected, result)
 
+    @pytest.mark.parametrize("periods, expected_vals", [
+        (1, [nan, nan, 1.0, 0.5, nan, 0.333333333333333, nan]),
+        (2, [nan, nan, nan, 2.0, nan, 1.0, nan])
+    ])
+    def test_pct_change_skipna(self, periods, expected_vals):
+        # GH25006
+        vals = [nan,  1.,  2.,  3., nan,  4., nan]
+        s = Series(vals)
+        result = s.pct_change(skipna=True, periods=periods)
+        expected = Series(expected_vals)
+        assert_series_equal(expected, result)
+
     def test_npdiff(self):
         pytest.skip("skipping due to Series no longer being an "
                     "ndarray")

From 192bded8f8bd67d787ad182695e78bed53da0ef6 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Wed, 13 Feb 2019 00:02:00 +0100
Subject: [PATCH 03/23] Fix PEP8 issues

---
 pandas/tests/frame/test_analytics.py  | 8 ++++----
 pandas/tests/series/test_analytics.py | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/pandas/tests/frame/test_analytics.py b/pandas/tests/frame/test_analytics.py
index 00d9835090c34..e4da742e81f62 100644
--- a/pandas/tests/frame/test_analytics.py
+++ b/pandas/tests/frame/test_analytics.py
@@ -1369,13 +1369,13 @@ def test_pct_change(self):
     @pytest.mark.parametrize("periods, expected_vals", [
         (1, [[nan, nan], [nan, nan], [1., nan], [0.5, 1.], [nan, 0.5],
              [0.33333333, nan], [nan, 0.33333333]]),
-        (2, [[nan, nan], [nan, nan], [nan, nan], [ 2., nan], [nan,  2.],
-             [ 1., nan], [nan,  1.]])
+        (2, [[nan, nan], [nan, nan], [nan, nan], [2., nan], [nan, 2.],
+             [1., nan], [nan, 1.]])
     ])
     def test_pct_change_skipna(self, periods, expected_vals):
         # GH25006
-        df = DataFrame([[nan, nan], [ 1., nan], [ 2.,  1.], [ 3.,  2.],
-                        [nan,  3.], [ 4., nan], [nan,  4.]])
+        df = DataFrame([[nan, nan], [1., nan], [2., 1.], [3., 2.],[nan, 3.],
+                        [4., nan], [nan, 4.]])
         result = df.pct_change(skipna=True, periods=periods)
         expected = DataFrame(expected_vals)
         assert_frame_equal(result, expected)
diff --git a/pandas/tests/series/test_analytics.py b/pandas/tests/series/test_analytics.py
index 4f65785412100..464453e1fbc04 100644
--- a/pandas/tests/series/test_analytics.py
+++ b/pandas/tests/series/test_analytics.py
@@ -218,7 +218,7 @@ def test_cummax_timedelta64(self):
     ])
     def test_pct_change_skipna(self, periods, expected_vals):
         # GH25006
-        vals = [nan,  1.,  2.,  3., nan,  4., nan]
+        vals = [nan, 1., 2., 3., nan, 4., nan]
         s = Series(vals)
         result = s.pct_change(skipna=True, periods=periods)
         expected = Series(expected_vals)

From bb74285834b4bb487ee54b63cffd658f7e3bdbcc Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Wed, 13 Feb 2019 07:24:34 +0100
Subject: [PATCH 04/23] Fix PEP8 issue

---
 pandas/tests/frame/test_analytics.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/frame/test_analytics.py b/pandas/tests/frame/test_analytics.py
index e4da742e81f62..ca605b72e6f15 100644
--- a/pandas/tests/frame/test_analytics.py
+++ b/pandas/tests/frame/test_analytics.py
@@ -1374,7 +1374,7 @@ def test_pct_change(self):
     ])
     def test_pct_change_skipna(self, periods, expected_vals):
         # GH25006
-        df = DataFrame([[nan, nan], [1., nan], [2., 1.], [3., 2.],[nan, 3.],
+        df = DataFrame([[nan, nan], [1., nan], [2., 1.], [3., 2.], [nan, 3.],
                         [4., nan], [nan, 4.]])
         result = df.pct_change(skipna=True, periods=periods)
         expected = DataFrame(expected_vals)

From 4418bf1e0a5fb1dc484c0d828fcb0d43a0cbb91b Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Wed, 13 Feb 2019 07:31:06 +0100
Subject: [PATCH 05/23] Fix test

---
 pandas/tests/frame/test_timeseries.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/frame/test_timeseries.py b/pandas/tests/frame/test_timeseries.py
index bc37317f72802..4055b9ff2895d 100644
--- a/pandas/tests/frame/test_timeseries.py
+++ b/pandas/tests/frame/test_timeseries.py
@@ -142,7 +142,7 @@ def test_pct_change_shift_over_nas(self):
 
         df = DataFrame({'a': s, 'b': s})
 
-        chg = df.pct_change()
+        chg = df.pct_change(fill_method='ffill')
         expected = Series([np.nan, 0.5, 0., 2.5 / 1.5 - 1, .2])
         edf = DataFrame({'a': expected, 'b': expected})
         assert_frame_equal(chg, edf)

From 3670ffe74197b4395611b49196ec51e97596730e Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Wed, 13 Feb 2019 07:34:35 +0100
Subject: [PATCH 06/23] Fix test

---
 pandas/tests/series/test_timeseries.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/series/test_timeseries.py b/pandas/tests/series/test_timeseries.py
index d082b023e1f27..5722b745809e0 100644
--- a/pandas/tests/series/test_timeseries.py
+++ b/pandas/tests/series/test_timeseries.py
@@ -399,7 +399,7 @@ def test_pct_change(self):
     def test_pct_change_shift_over_nas(self):
         s = Series([1., 1.5, np.nan, 2.5, 3.])
 
-        chg = s.pct_change()
+        chg = s.pct_change(fill_method='ffill')
         expected = Series([np.nan, 0.5, 0., 2.5 / 1.5 - 1, .2])
         assert_series_equal(chg, expected)
 

From 8f36c7aea348c5d50df62510cf086c8c7a28f637 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Wed, 13 Feb 2019 23:38:13 +0100
Subject: [PATCH 07/23] Fix tests

---
 pandas/tests/frame/test_analytics.py  | 16 +++++------
 pandas/tests/generic/test_generic.py  | 11 +++++---
 pandas/tests/series/test_analytics.py | 39 +++++++++++++--------------
 3 files changed, 32 insertions(+), 34 deletions(-)

diff --git a/pandas/tests/frame/test_analytics.py b/pandas/tests/frame/test_analytics.py
index ca605b72e6f15..ea8a20bec0aa2 100644
--- a/pandas/tests/frame/test_analytics.py
+++ b/pandas/tests/frame/test_analytics.py
@@ -6,7 +6,6 @@
 import warnings
 
 import numpy as np
-from numpy import nan
 import pytest
 
 from pandas.compat import PY35, lrange
@@ -19,7 +18,6 @@
 import pandas.core.algorithms as algorithms
 import pandas.core.nanops as nanops
 import pandas.util.testing as tm
-from pandas.util.testing import (assert_frame_equal)
 
 
 def assert_stat_op_calc(opname, alternative, frame, has_skipna=True,
@@ -1367,18 +1365,18 @@ def test_pct_change(self):
             tm.assert_frame_equal(result, expected)
 
     @pytest.mark.parametrize("periods, expected_vals", [
-        (1, [[nan, nan], [nan, nan], [1., nan], [0.5, 1.], [nan, 0.5],
-             [0.33333333, nan], [nan, 0.33333333]]),
-        (2, [[nan, nan], [nan, nan], [nan, nan], [2., nan], [nan, 2.],
-             [1., nan], [nan, 1.]])
+        (1, [[np.nan, np.nan], [np.nan, np.nan], [1., np.nan], [0.5, 1.],
+             [np.nan, 0.5], [0.33333333, np.nan], [np.nan, 0.33333333]]),
+        (2, [[np.nan, np.nan], [np.nan, np.nan], [np.nan, np.nan],
+             [2., np.nan], [np.nan, 2.], [1., np.nan], [np.nan, 1.]])
     ])
     def test_pct_change_skipna(self, periods, expected_vals):
         # GH25006
-        df = DataFrame([[nan, nan], [1., nan], [2., 1.], [3., 2.], [nan, 3.],
-                        [4., nan], [nan, 4.]])
+        df = DataFrame([[np.nan, np.nan], [1., np.nan], [2., 1.], [3., 2.],
+                        [np.nan, 3.], [4., np.nan], [np.nan, 4.]])
         result = df.pct_change(skipna=True, periods=periods)
         expected = DataFrame(expected_vals)
-        assert_frame_equal(result, expected)
+        tm.assert_frame_equal(result, expected)
 
 
     # ----------------------------------------------------------------------
diff --git a/pandas/tests/generic/test_generic.py b/pandas/tests/generic/test_generic.py
index 8b29b4f8dbe39..bca4b2fa21de8 100644
--- a/pandas/tests/generic/test_generic.py
+++ b/pandas/tests/generic/test_generic.py
@@ -618,10 +618,13 @@ def test_pct_change(self, periods, fill_method, limit, exp):
     ])
     def test_pct_change_skipna_error(self, fill_method, limit):
         # GH25006
-        vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
-        obj = self._typ(vals)
-        _ = obj.pct_change(skipna=True, fill_method=fill_method, limit=limit)
-        assert True
+        if self._typ is DataFrame or self._typ is Series:
+            vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
+            obj = self._typ(vals)
+            _ = obj.pct_change(skipna=True, fill_method=fill_method, limit=limit)
+            assert False
+        else:
+            raise ValueError()
 
 class TestNDFrame(object):
     # tests that don't fit elsewhere
diff --git a/pandas/tests/series/test_analytics.py b/pandas/tests/series/test_analytics.py
index 464453e1fbc04..fefff8bda8234 100644
--- a/pandas/tests/series/test_analytics.py
+++ b/pandas/tests/series/test_analytics.py
@@ -6,7 +6,6 @@
 import operator
 
 import numpy as np
-from numpy import nan
 import pytest
 
 from pandas.compat import PY35, lrange, range
@@ -213,12 +212,12 @@ def test_cummax_timedelta64(self):
         tm.assert_series_equal(expected, result)
 
     @pytest.mark.parametrize("periods, expected_vals", [
-        (1, [nan, nan, 1.0, 0.5, nan, 0.333333333333333, nan]),
-        (2, [nan, nan, nan, 2.0, nan, 1.0, nan])
+        (1, [np.nan, np.nan, 1.0, 0.5, np.nan, 0.333333333333333, np.nan]),
+        (2, [np.nan, np.nan, np.nan, 2.0, np.nan, 1.0, np.nan])
     ])
     def test_pct_change_skipna(self, periods, expected_vals):
         # GH25006
-        vals = [nan, 1., 2., 3., nan, 4., nan]
+        vals = [np.nan, 1., 2., 3., np.nan, 4., np.nan]
         s = Series(vals)
         result = s.pct_change(skipna=True, periods=periods)
         expected = Series(expected_vals)
@@ -232,7 +231,7 @@ def test_npdiff(self):
         s = Series(np.arange(5))
 
         r = np.diff(s)
-        assert_series_equal(Series([nan, 0, 0, 0, nan]), r)
+        assert_series_equal(Series([np.nan, 0, 0, 0, np.nan]), r)
 
     def _check_accum_op(self, name, datetime_series_, check_dtype=True):
         func = getattr(np, name)
@@ -457,14 +456,14 @@ def test_count(self, datetime_series):
 
         assert datetime_series.count() == np.isfinite(datetime_series).sum()
 
-        mi = MultiIndex.from_arrays([list('aabbcc'), [1, 2, 2, nan, 1, 2]])
+        mi = MultiIndex.from_arrays([list('aabbcc'), [1, 2, 2, np.nan, 1, 2]])
         ts = Series(np.arange(len(mi)), index=mi)
 
         left = ts.count(level=1)
-        right = Series([2, 3, 1], index=[1, 2, nan])
+        right = Series([2, 3, 1], index=[1, 2, np.nan])
         assert_series_equal(left, right)
 
-        ts.iloc[[0, 3, 5]] = nan
+        ts.iloc[[0, 3, 5]] = np.nan
         assert_series_equal(ts.count(level=1), right - 1)
 
     def test_dot(self):
@@ -685,11 +684,11 @@ def test_cummethods_bool(self):
             result = getattr(s, method)()
             assert_series_equal(result, expected)
 
-        e = pd.Series([False, True, nan, False])
-        cse = pd.Series([0, 1, nan, 1], dtype=object)
-        cpe = pd.Series([False, 0, nan, 0])
-        cmin = pd.Series([False, False, nan, False])
-        cmax = pd.Series([False, True, nan, True])
+        e = pd.Series([False, True, np.nan, False])
+        cse = pd.Series([0, 1, np.nan, 1], dtype=object)
+        cpe = pd.Series([False, 0, np.nan, 0])
+        cmin = pd.Series([False, False, np.nan, False])
+        cmax = pd.Series([False, True, np.nan, True])
         expecteds = {'cumsum': cse,
                      'cumprod': cpe,
                      'cummin': cmin,
@@ -966,15 +965,13 @@ def test_shift_categorical(self):
         assert_index_equal(s.values.categories, sn2.values.categories)
 
     def test_unstack(self):
-        from numpy import nan
-
         index = MultiIndex(levels=[['bar', 'foo'], ['one', 'three', 'two']],
                            codes=[[1, 1, 0, 0], [0, 1, 0, 2]])
 
         s = Series(np.arange(4.), index=index)
         unstacked = s.unstack()
 
-        expected = DataFrame([[2., nan, 3.], [0., 1., nan]],
+        expected = DataFrame([[2., np.nan, 3.], [0., 1., np.nan]],
                              index=['bar', 'foo'],
                              columns=['one', 'three', 'two'])
 
@@ -998,17 +995,17 @@ def test_unstack(self):
         idx = pd.MultiIndex.from_arrays([[101, 102], [3.5, np.nan]])
         ts = pd.Series([1, 2], index=idx)
         left = ts.unstack()
-        right = DataFrame([[nan, 1], [2, nan]], index=[101, 102],
-                          columns=[nan, 3.5])
+        right = DataFrame([[np.nan, 1], [2, np.nan]], index=[101, 102],
+                          columns=[np.nan, 3.5])
         assert_frame_equal(left, right)
 
         idx = pd.MultiIndex.from_arrays([['cat', 'cat', 'cat', 'dog', 'dog'
                                           ], ['a', 'a', 'b', 'a', 'b'],
                                          [1, 2, 1, 1, np.nan]])
         ts = pd.Series([1.0, 1.1, 1.2, 1.3, 1.4], index=idx)
-        right = DataFrame([[1.0, 1.3], [1.1, nan], [nan, 1.4], [1.2, nan]],
-                          columns=['cat', 'dog'])
-        tpls = [('a', 1), ('a', 2), ('b', nan), ('b', 1)]
+        right = DataFrame([[1.0, 1.3], [1.1, np.nan], [np.nan, 1.4],
+                           [1.2, np.nan]], columns=['cat', 'dog'])
+        tpls = [('a', 1), ('a', 2), ('b', np.nan), ('b', 1)]
         right.index = pd.MultiIndex.from_tuples(tpls)
         assert_frame_equal(ts.unstack(level=0), right)
 

From add18de0a9e285dad49c9f89664b6a10e1985ef8 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Thu, 14 Feb 2019 07:04:04 +0100
Subject: [PATCH 08/23] Fix linting

---
 pandas/tests/frame/test_analytics.py | 1 -
 pandas/tests/generic/test_generic.py | 6 ++++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/pandas/tests/frame/test_analytics.py b/pandas/tests/frame/test_analytics.py
index ea8a20bec0aa2..d2293b0085afa 100644
--- a/pandas/tests/frame/test_analytics.py
+++ b/pandas/tests/frame/test_analytics.py
@@ -1378,7 +1378,6 @@ def test_pct_change_skipna(self, periods, expected_vals):
         expected = DataFrame(expected_vals)
         tm.assert_frame_equal(result, expected)
 
-
     # ----------------------------------------------------------------------
     # Index of max / min
 
diff --git a/pandas/tests/generic/test_generic.py b/pandas/tests/generic/test_generic.py
index bca4b2fa21de8..a87d38d72430b 100644
--- a/pandas/tests/generic/test_generic.py
+++ b/pandas/tests/generic/test_generic.py
@@ -621,11 +621,13 @@ def test_pct_change_skipna_error(self, fill_method, limit):
         if self._typ is DataFrame or self._typ is Series:
             vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
             obj = self._typ(vals)
-            _ = obj.pct_change(skipna=True, fill_method=fill_method, limit=limit)
-            assert False
+            result = obj.pct_change(skipna=True, fill_method=fill_method,
+                               limit=limit)
+            assert result is False
         else:
             raise ValueError()
 
+
 class TestNDFrame(object):
     # tests that don't fit elsewhere
 

From 279f433c62a79b2ea57d97ef03b0267bea4a5ed4 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Wed, 20 Feb 2019 23:45:17 +0100
Subject: [PATCH 09/23] Set default skipna=True

---
 pandas/core/generic.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 805398f37b548..2d8c4944a9c0b 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -9954,21 +9954,21 @@ def _check_percentile(self, q):
 
     @Appender(_shared_docs['pct_change'] % _shared_doc_kwargs)
     def pct_change(self, periods=1, fill_method=None, limit=None, freq=None,
-                   skipna=False, **kwargs):
+                   skipna=None, **kwargs):
         if skipna and fill_method is not None:
             raise ValueError("cannot pass both skipna and fill_method")
         elif skipna and limit is not None:
             raise ValueError("cannot pass both skipna and limit")
+        if skipna is None and fill_method is None and limit is None:
+            skipna = True
         if skipna and self._typ == 'dataframe':
             return self.apply(
-                lambda s: s.pct_change(periods=periods,
-                                       fill_method=fill_method, limit=limit,
-                                       freq=freq, skipna=skipna, **kwargs)
+                lambda s: s.pct_change(periods=periods, freq=freq,
+                                       skipna=skipna, **kwargs)
             )
         # TODO: Not sure if above is correct - need someone to confirm.
         axis = self._get_axis_number(kwargs.pop('axis', self._stat_axis_name))
         if skipna:
-            # mask = self.isna()
             data = self.dropna()
         elif fill_method is None:
             data = self

From 4072ca0cbf9875e24700fa99aabd55dafc64533f Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Wed, 20 Feb 2019 23:46:12 +0100
Subject: [PATCH 10/23] Use pytest.raises

---
 pandas/tests/generic/test_generic.py | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/pandas/tests/generic/test_generic.py b/pandas/tests/generic/test_generic.py
index aea5258297175..2407a7c7cd214 100644
--- a/pandas/tests/generic/test_generic.py
+++ b/pandas/tests/generic/test_generic.py
@@ -607,7 +607,6 @@ def test_pct_change(self, periods, fill_method, limit, exp):
         else:
             tm.assert_series_equal(res, Series(exp))
 
-    @pytest.mark.xfail(raises=ValueError)
     @pytest.mark.parametrize('fill_method, limit', [
         ('backfill', None),
         ('bfill', None),
@@ -615,16 +614,14 @@ def test_pct_change(self, periods, fill_method, limit, exp):
         ('ffill', None),
         (None, 1)
     ])
-    def test_pct_change_skipna_error(self, fill_method, limit):
+    def test_pct_change_skipna_raises(self, fill_method, limit):
         # GH25006
         if self._typ is DataFrame or self._typ is Series:
             vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
             obj = self._typ(vals)
-            result = obj.pct_change(skipna=True, fill_method=fill_method,
+            with pytest.raises(ValueError):
+                obj.pct_change(skipna=True, fill_method=fill_method,
                                limit=limit)
-            assert result is False
-        else:
-            raise ValueError()
 
 
 class TestNDFrame(object):

From 80a09c9e48caf1a8a742dc6c4a41f3beb9769adf Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Sat, 2 Mar 2019 09:53:57 +0100
Subject: [PATCH 11/23] Address requested changes

---
 pandas/core/generic.py               | 24 +++++++++++++++++++-----
 pandas/tests/frame/test_analytics.py | 20 +++++++++++++-------
 pandas/tests/generic/test_generic.py | 15 +++++++++------
 3 files changed, 41 insertions(+), 18 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index b54d143e7813d..62d5003b27d84 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -9845,6 +9845,8 @@ def _check_percentile(self, q):
 
         Parameters
         ----------
+        skipna : bool, default True
+            Exclude NA/null values before computing percent change.
         periods : int, default 1
             Periods to shift for forming percent change.
         fill_method : str, default 'pad'
@@ -9892,8 +9894,9 @@ def _check_percentile(self, q):
         2   -0.055556
         dtype: float64
 
-        See the percentage change in a Series where filling NAs with last
-        valid observation forward to next valid.
+        See the computing of percentage change in a Series with NAs. With
+        default skipped NAs, NAs are ignored before the computation and kept
+        afterwards.
 
         >>> s = pd.Series([90, 91, None, 85])
         >>> s
@@ -9903,6 +9906,17 @@ def _check_percentile(self, q):
         3    85.0
         dtype: float64
 
+        >>> s.pct_change()
+        0         NaN
+        1    0.011111
+        2         NaN
+        3   -0.065934
+        dtype: float64
+
+        On the other hand, if a fill method is set, NAs are filled before the
+        computation. See forward fill method fills NAs with last valid
+        observation forward to next valid.
+
         >>> s.pct_change(fill_method='ffill')
         0         NaN
         1    0.011111
@@ -9952,15 +9966,15 @@ def _check_percentile(self, q):
         """
 
     @Appender(_shared_docs['pct_change'] % _shared_doc_kwargs)
-    def pct_change(self, periods=1, fill_method=None, limit=None, freq=None,
-                   skipna=None, **kwargs):
+    def pct_change(self, skipna=None, periods=1, fill_method=None, limit=None,
+                   freq=None, **kwargs):
         if skipna and fill_method is not None:
             raise ValueError("cannot pass both skipna and fill_method")
         elif skipna and limit is not None:
             raise ValueError("cannot pass both skipna and limit")
         if skipna is None and fill_method is None and limit is None:
             skipna = True
-        if skipna and self._typ == 'dataframe':
+        if skipna and isinstance(self, pd.DataFrame):
             return self.apply(
                 lambda s: s.pct_change(periods=periods, freq=freq,
                                        skipna=skipna, **kwargs)
diff --git a/pandas/tests/frame/test_analytics.py b/pandas/tests/frame/test_analytics.py
index e5aa3272e0aa5..a5d20a3d4f58e 100644
--- a/pandas/tests/frame/test_analytics.py
+++ b/pandas/tests/frame/test_analytics.py
@@ -1364,17 +1364,23 @@ def test_pct_change(self):
 
             tm.assert_frame_equal(result, expected)
 
-    @pytest.mark.parametrize("periods, expected_vals", [
-        (1, [[np.nan, np.nan], [np.nan, np.nan], [1., np.nan], [0.5, 1.],
-             [np.nan, 0.5], [0.33333333, np.nan], [np.nan, 0.33333333]]),
-        (2, [[np.nan, np.nan], [np.nan, np.nan], [np.nan, np.nan],
-             [2., np.nan], [np.nan, 2.], [1., np.nan], [np.nan, 1.]])
+    @pytest.mark.parametrize("skipna, periods, expected_vals", [
+        (True, 1, [[np.nan, np.nan], [np.nan, np.nan], [1., np.nan], [0.5, 1.],
+                   [np.nan, 0.5], [0.33333333, np.nan], [np.nan, 0.33333333]]),
+        (True, 2, [[np.nan, np.nan], [np.nan, np.nan], [np.nan, np.nan],
+                   [2., np.nan], [np.nan, 2.], [1., np.nan], [np.nan, 1.]]),
+        (False, 1, [[np.nan, np.nan], [np.nan, np.nan], [1., np.nan],
+                    [0.5, 1.], [np.nan, 0.5], [np.nan, np.nan],
+                    [np.nan, np.nan]]),
+        (False, 2, [[np.nan, np.nan], [np.nan, np.nan], [np.nan, np.nan],
+                    [2., np.nan], [np.nan, 2.], [0.33333333, np.nan],
+                    [np.nan, 0.33333333]])
     ])
-    def test_pct_change_skipna(self, periods, expected_vals):
+    def test_pct_change_skipna(self, skipna, periods, expected_vals):
         # GH25006
         df = DataFrame([[np.nan, np.nan], [1., np.nan], [2., 1.], [3., 2.],
                         [np.nan, 3.], [4., np.nan], [np.nan, 4.]])
-        result = df.pct_change(skipna=True, periods=periods)
+        result = df.pct_change(skipna=skipna, periods=periods)
         expected = DataFrame(expected_vals)
         tm.assert_frame_equal(result, expected)
 
diff --git a/pandas/tests/generic/test_generic.py b/pandas/tests/generic/test_generic.py
index 2407a7c7cd214..317ba5d4337ba 100644
--- a/pandas/tests/generic/test_generic.py
+++ b/pandas/tests/generic/test_generic.py
@@ -616,12 +616,15 @@ def test_pct_change(self, periods, fill_method, limit, exp):
     ])
     def test_pct_change_skipna_raises(self, fill_method, limit):
         # GH25006
-        if self._typ is DataFrame or self._typ is Series:
-            vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
-            obj = self._typ(vals)
-            with pytest.raises(ValueError):
-                obj.pct_change(skipna=True, fill_method=fill_method,
-                               limit=limit)
+        vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
+        obj = self._typ(vals)
+        if fill_method:
+            msg = "cannot pass both skipna and fill_method"
+        else:
+            msg = "cannot pass both skipna and limit"
+        with pytest.raises(ValueError, match=msg):
+            obj.pct_change(skipna=True, fill_method=fill_method,
+                           limit=limit)
 
 
 class TestNDFrame(object):

From 1bf00f81466e7e1ee30ae42a8529caec9dd073f1 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Sat, 2 Mar 2019 11:22:10 +0100
Subject: [PATCH 12/23] Fix tests passing periods as kwarg

---
 pandas/tests/frame/test_timeseries.py  | 8 ++++----
 pandas/tests/series/test_timeseries.py | 6 +++---
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/pandas/tests/frame/test_timeseries.py b/pandas/tests/frame/test_timeseries.py
index 620ec2cb08435..ec6114d13e065 100644
--- a/pandas/tests/frame/test_timeseries.py
+++ b/pandas/tests/frame/test_timeseries.py
@@ -121,10 +121,10 @@ def test_diff_axis(self):
             [[np.nan, np.nan], [2., 2.]]))
 
     def test_pct_change(self):
-        rs = self.tsframe.pct_change(fill_method=None)
+        rs = self.tsframe.pct_change(skipna=False, fill_method=None)
         assert_frame_equal(rs, self.tsframe / self.tsframe.shift(1) - 1)
 
-        rs = self.tsframe.pct_change(2)
+        rs = self.tsframe.pct_change(periods=2)
         filled = self.tsframe.fillna(method='pad')
         assert_frame_equal(rs, filled / filled.shift(2) - 1)
 
@@ -160,7 +160,7 @@ def test_pct_change_periods_freq(self, freq, periods, fill_method, limit):
         rs_freq = self.tsframe.pct_change(freq=freq,
                                           fill_method=fill_method,
                                           limit=limit)
-        rs_periods = self.tsframe.pct_change(periods,
+        rs_periods = self.tsframe.pct_change(periods=periods,
                                              fill_method=fill_method,
                                              limit=limit)
         assert_frame_equal(rs_freq, rs_periods)
@@ -170,7 +170,7 @@ def test_pct_change_periods_freq(self, freq, periods, fill_method, limit):
         rs_freq = empty_ts.pct_change(freq=freq,
                                       fill_method=fill_method,
                                       limit=limit)
-        rs_periods = empty_ts.pct_change(periods,
+        rs_periods = empty_ts.pct_change(periods=periods,
                                          fill_method=fill_method,
                                          limit=limit)
         assert_frame_equal(rs_freq, rs_periods)
diff --git a/pandas/tests/series/test_timeseries.py b/pandas/tests/series/test_timeseries.py
index 5722b745809e0..ed5912bc95d5e 100644
--- a/pandas/tests/series/test_timeseries.py
+++ b/pandas/tests/series/test_timeseries.py
@@ -382,7 +382,7 @@ def test_pct_change(self):
         rs = self.ts.pct_change(fill_method=None)
         assert_series_equal(rs, self.ts / self.ts.shift(1) - 1)
 
-        rs = self.ts.pct_change(2)
+        rs = self.ts.pct_change(periods=2)
         filled = self.ts.fillna(method='pad')
         assert_series_equal(rs, filled / filled.shift(2) - 1)
 
@@ -415,7 +415,7 @@ def test_pct_change_periods_freq(self, freq, periods, fill_method, limit):
         rs_freq = self.ts.pct_change(freq=freq,
                                      fill_method=fill_method,
                                      limit=limit)
-        rs_periods = self.ts.pct_change(periods,
+        rs_periods = self.ts.pct_change(periods=periods,
                                         fill_method=fill_method,
                                         limit=limit)
         assert_series_equal(rs_freq, rs_periods)
@@ -424,7 +424,7 @@ def test_pct_change_periods_freq(self, freq, periods, fill_method, limit):
         rs_freq = empty_ts.pct_change(freq=freq,
                                       fill_method=fill_method,
                                       limit=limit)
-        rs_periods = empty_ts.pct_change(periods,
+        rs_periods = empty_ts.pct_change(periods=periods,
                                          fill_method=fill_method,
                                          limit=limit)
         assert_series_equal(rs_freq, rs_periods)

From 66cc4a423dc19891cd4a4a968717f98087def1d3 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Sun, 3 Mar 2019 18:09:38 +0100
Subject: [PATCH 13/23] Add whatsnew note

---
 doc/source/whatsnew/v0.25.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v0.25.0.rst b/doc/source/whatsnew/v0.25.0.rst
index 124ec8f4ab92c..0ca3a7d840762 100644
--- a/doc/source/whatsnew/v0.25.0.rst
+++ b/doc/source/whatsnew/v0.25.0.rst
@@ -86,6 +86,7 @@ Other API Changes
 - :class:`DatetimeTZDtype` will now standardize pytz timezones to a common timezone instance (:issue:`24713`)
 - ``Timestamp`` and ``Timedelta`` scalars now implement the :meth:`to_numpy` method as aliases to :meth:`Timestamp.to_datetime64` and :meth:`Timedelta.to_timedelta64`, respectively. (:issue:`24653`)
 - :meth:`Timestamp.strptime` will now rise a ``NotImplementedError`` (:issue:`25016`)
+- Default `skipna=True` for :meth:`Series.pct_change` and :meth:`DataFrame.pct_change` will drop NAs before calculation (:issue:`25006`)
 -
 
 .. _whatsnew_0250.deprecations:

From 14c7a05fe2ab16728f8c8c0777c10ac58a537e0b Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Sun, 3 Mar 2019 18:13:17 +0100
Subject: [PATCH 14/23] Fix for the case axis=1

---
 pandas/core/generic.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 362ae210679ac..373da84b286cf 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -9986,13 +9986,14 @@ def pct_change(self, skipna=None, periods=1, fill_method=None, limit=None,
             raise ValueError("cannot pass both skipna and limit")
         if skipna is None and fill_method is None and limit is None:
             skipna = True
+        axis = self._get_axis_number(kwargs.pop('axis', self._stat_axis_name))
         if skipna and isinstance(self, pd.DataFrame):
+            # If DataFrame, apply to each column/row
             return self.apply(
                 lambda s: s.pct_change(periods=periods, freq=freq,
-                                       skipna=skipna, **kwargs)
+                                       skipna=skipna, **kwargs),
+                axis=axis
             )
-        # TODO: Not sure if above is correct - need someone to confirm.
-        axis = self._get_axis_number(kwargs.pop('axis', self._stat_axis_name))
         if skipna:
             data = self.dropna()
         elif fill_method is None:

From 932fc6651ce7ec80c198779cdebe509bd78526d6 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Sun, 3 Mar 2019 18:14:16 +0100
Subject: [PATCH 15/23] Address requested changes

---
 pandas/core/generic.py               | 92 +++++++++++++++++++++++-----
 pandas/tests/generic/test_generic.py |  4 +-
 2 files changed, 79 insertions(+), 17 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 373da84b286cf..153f2a286b94c 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -9857,8 +9857,6 @@ def _check_percentile(self, q):
 
         Parameters
         ----------
-        skipna : bool, default True
-            Exclude NA/null values before computing percent change.
         periods : int, default 1
             Periods to shift for forming percent change.
         fill_method : str, default 'pad'
@@ -9867,6 +9865,10 @@ def _check_percentile(self, q):
             The number of consecutive NAs to fill before stopping.
         freq : DateOffset, timedelta, or offset alias string, optional
             Increment to use from time series API (e.g. 'M' or BDay()).
+        skipna : bool, default True
+            Exclude NA/null values before computing percent change.
+
+            .. versionadded:: 0.25.0
         **kwargs
             Additional keyword arguments are passed into
             `DataFrame.shift` or `Series.shift`.
@@ -9883,6 +9885,11 @@ def _check_percentile(self, q):
         Series.shift : Shift the index by some number of periods.
         DataFrame.shift : Shift the index by some number of periods.
 
+        Notes
+        -----
+        The default `skipna=True` drops NAs before computing the percentage
+        change, and the results are reindexed like the original calling object.
+
         Examples
         --------
         **Series**
@@ -9906,16 +9913,19 @@ def _check_percentile(self, q):
         2   -0.055556
         dtype: float64
 
-        See the computing of percentage change in a Series with NAs. With
-        default skipped NAs, NAs are ignored before the computation and kept
-        afterwards.
+        See how the computing of percentage change is performed in a Series
+        with NAs. With default `skipna=True`, NAs are dropped before the
+        computation and eventually the results are reindexed like the original
+        object, thus keeping the original NAs.
 
-        >>> s = pd.Series([90, 91, None, 85])
+        >>> s = pd.Series([90, 91, None, 85, None, 95])
         >>> s
         0    90.0
         1    91.0
         2     NaN
         3    85.0
+        4     NaN
+        5    95.0
         dtype: float64
 
         >>> s.pct_change()
@@ -9923,10 +9933,13 @@ def _check_percentile(self, q):
         1    0.011111
         2         NaN
         3   -0.065934
+        4         NaN
+        5    0.117647
         dtype: float64
 
-        On the other hand, if a fill method is set, NAs are filled before the
-        computation. See forward fill method fills NAs with last valid
+        On the other hand, if a fill method is passed, NAs are filled before
+        the computation. For example, before the computation of percentage
+        change, forward fill method `ffill` first fills NAs with last valid
         observation forward to next valid.
 
         >>> s.pct_change(fill_method='ffill')
@@ -9934,6 +9947,8 @@ def _check_percentile(self, q):
         1    0.011111
         2    0.000000
         3   -0.065934
+        4    0.000000
+        5    0.117647
         dtype: float64
 
         **DataFrame**
@@ -9975,16 +9990,63 @@ def _check_percentile(self, q):
               2016      2015      2014
         GOOG   NaN -0.151997 -0.086016
         APPL   NaN  0.337604  0.012002
+
+        In a DataFrame with NAs, when computing the percentage change with
+        default `skipna=True`, NAs are first droppped on each column/row, and
+        the results are eventually reindexed as originally.
+
+        >>> df = pd.DataFrame({
+        ...     'a': [90, 91, None, 85, None, 95],
+        ...     'b': [91, None, 85, None, 95, None],
+        ...     'c': [None, 85, None, 95, None, None]})
+        >>> df
+              a     b     c
+        0  90.0  91.0   NaN
+        1  91.0   NaN  85.0
+        2   NaN  85.0   NaN
+        3  85.0   NaN  95.0
+        4   NaN  95.0   NaN
+        5  95.0   NaN   NaN
+
+        >>> df.pct_change()
+                  a         b         c
+        0       NaN       NaN       NaN
+        1  0.011111       NaN       NaN
+        2       NaN -0.065934       NaN
+        3 -0.065934       NaN  0.117647
+        4       NaN  0.117647       NaN
+        5  0.117647       NaN       NaN
+
+        >>> df.pct_change(axis=1)
+            a         b         c
+        0 NaN  0.011111       NaN
+        1 NaN       NaN -0.065934
+        2 NaN       NaN       NaN
+        3 NaN       NaN  0.117647
+        4 NaN       NaN       NaN
+        5 NaN       NaN       NaN
+
+        Otherwise, if a fill method is passed, NAs are filled before the
+        computation.
+
+        >>> df.pct_change(fill_method='ffill')
+                  a         b         c
+        0       NaN       NaN       NaN
+        1  0.011111  0.000000       NaN
+        2  0.000000 -0.065934  0.000000
+        3 -0.065934  0.000000  0.117647
+        4  0.000000  0.117647  0.000000
+        5  0.117647  0.000000  0.000000
         """
 
     @Appender(_shared_docs['pct_change'] % _shared_doc_kwargs)
-    def pct_change(self, skipna=None, periods=1, fill_method=None, limit=None,
-                   freq=None, **kwargs):
-        if skipna and fill_method is not None:
-            raise ValueError("cannot pass both skipna and fill_method")
-        elif skipna and limit is not None:
-            raise ValueError("cannot pass both skipna and limit")
-        if skipna is None and fill_method is None and limit is None:
+    def pct_change(self, periods=1, fill_method=None, limit=None, freq=None,
+                   skipna=None, **kwargs):
+        if fill_method is not None and skipna:
+            raise ValueError("cannot pass both fill_method and skipna")
+        elif limit is not None and skipna:
+            raise ValueError("cannot pass both limit and skipna")
+        if fill_method is None and limit is None and skipna is None:
             skipna = True
         axis = self._get_axis_number(kwargs.pop('axis', self._stat_axis_name))
         if skipna and isinstance(self, pd.DataFrame):
diff --git a/pandas/tests/generic/test_generic.py b/pandas/tests/generic/test_generic.py
index 317ba5d4337ba..9adbed76aa96b 100644
--- a/pandas/tests/generic/test_generic.py
+++ b/pandas/tests/generic/test_generic.py
@@ -619,9 +619,9 @@ def test_pct_change_skipna_raises(self, fill_method, limit):
         vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
         obj = self._typ(vals)
         if fill_method:
-            msg = "cannot pass both skipna and fill_method"
+            msg = "cannot pass both fill_method and skipna"
         else:
-            msg = "cannot pass both skipna and limit"
+            msg = "cannot pass both limit and skipna"
         with pytest.raises(ValueError, match=msg):
             obj.pct_change(skipna=True, fill_method=fill_method,
                            limit=limit)

From ed86a7bb53aa58d73d953c5f434a0a9ef51b0e94 Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Sat, 16 Mar 2019 17:10:50 +0100
Subject: [PATCH 16/23] Replace None with np.nan

---
 pandas/core/generic.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 153f2a286b94c..6e8b198f5d164 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -9918,7 +9918,7 @@ def _check_percentile(self, q):
         computation and eventually the results are reindexed like the original
         object, thus keeping the original NAs.
 
-        >>> s = pd.Series([90, 91, None, 85, None, 95])
+        >>> s = pd.Series([90, 91, np.nan, 85, np.nan, 95])
         >>> s
         0    90.0
         1    91.0
@@ -9996,9 +9996,9 @@ def _check_percentile(self, q):
         the results are eventually reindexed as originally.
 
         >>> df = pd.DataFrame({
-        ...     'a': [90, 91, None, 85, None, 95],
-        ...     'b': [91, None, 85, None, 95, None],
-        ...     'c': [None, 85, None, 95, None, None]})
+        ...     'a': [90, 91, np.nan, 85, np.nan, 95],
+        ...     'b': [91, np.nan, 85, np.nan, 95, np.nan],
+        ...     'c': [np.nan, 85, np.nan, 95, np.nan, np.nan]})
         >>> df
               a     b     c
         0  90.0  91.0   NaN

From a1ca0ca8e026ea47b83897fe3bce2b5477ea7f3c Mon Sep 17 00:00:00 2001
From: Albert Villanova del Moral <albert.villanova@gmail.com>
Date: Sat, 16 Mar 2019 17:42:01 +0100
Subject: [PATCH 17/23] Replace DataFrame with ABCDataFrame

---
 pandas/core/generic.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 6e8b198f5d164..4d82b7f49ebd4 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -10049,7 +10049,7 @@ def pct_change(self, periods=1, fill_method=None, limit=None, freq=None,
         if fill_method is None and limit is None and skipna is None:
             skipna = True
         axis = self._get_axis_number(kwargs.pop('axis', self._stat_axis_name))
-        if skipna and isinstance(self, pd.DataFrame):
+        if skipna and isinstance(self, ABCDataFrame):
             # If DataFrame, apply to each column/row
             return self.apply(
                 lambda s: s.pct_change(periods=periods, freq=freq,

From 1acee7ca58cd2f121729a94da08fabd5248300c9 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Sun, 25 Aug 2019 19:39:33 -0700
Subject: [PATCH 18/23] blackify

---
 pandas/core/generic.py                 |  7 ++-
 pandas/tests/frame/test_analytics.py   | 82 +++++++++++++++++++++-----
 pandas/tests/frame/test_timeseries.py  |  4 +-
 pandas/tests/generic/test_generic.py   | 20 ++++---
 pandas/tests/series/test_analytics.py  | 20 ++++---
 pandas/tests/series/test_timeseries.py |  8 ++-
 6 files changed, 105 insertions(+), 36 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 66809a2d08091..85fc4c102e955 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -10456,9 +10456,10 @@ def pct_change(self, periods=1, fill_method="pad", limit=None, freq=None, **kwar
         if skipna and isinstance(self, ABCDataFrame):
             # If DataFrame, apply to each column/row
             return self.apply(
-                lambda s: s.pct_change(periods=periods, freq=freq,
-                                       skipna=skipna, **kwargs),
-                axis=axis
+                lambda s: s.pct_change(
+                    periods=periods, freq=freq, skipna=skipna, **kwargs
+                ),
+                axis=axis,
             )
         if skipna:
             data = self.dropna()
diff --git a/pandas/tests/frame/test_analytics.py b/pandas/tests/frame/test_analytics.py
index 18d19e35e6d4d..56d310006927b 100644
--- a/pandas/tests/frame/test_analytics.py
+++ b/pandas/tests/frame/test_analytics.py
@@ -1627,22 +1627,76 @@ def test_pct_change(self):
 
             tm.assert_frame_equal(result, expected)
 
-    @pytest.mark.parametrize("skipna, periods, expected_vals", [
-        (True, 1, [[np.nan, np.nan], [np.nan, np.nan], [1., np.nan], [0.5, 1.],
-                   [np.nan, 0.5], [0.33333333, np.nan], [np.nan, 0.33333333]]),
-        (True, 2, [[np.nan, np.nan], [np.nan, np.nan], [np.nan, np.nan],
-                   [2., np.nan], [np.nan, 2.], [1., np.nan], [np.nan, 1.]]),
-        (False, 1, [[np.nan, np.nan], [np.nan, np.nan], [1., np.nan],
-                    [0.5, 1.], [np.nan, 0.5], [np.nan, np.nan],
-                    [np.nan, np.nan]]),
-        (False, 2, [[np.nan, np.nan], [np.nan, np.nan], [np.nan, np.nan],
-                    [2., np.nan], [np.nan, 2.], [0.33333333, np.nan],
-                    [np.nan, 0.33333333]])
-    ])
+    @pytest.mark.parametrize(
+        "skipna, periods, expected_vals",
+        [
+            (
+                True,
+                1,
+                [
+                    [np.nan, np.nan],
+                    [np.nan, np.nan],
+                    [1.0, np.nan],
+                    [0.5, 1.0],
+                    [np.nan, 0.5],
+                    [0.33333333, np.nan],
+                    [np.nan, 0.33333333],
+                ],
+            ),
+            (
+                True,
+                2,
+                [
+                    [np.nan, np.nan],
+                    [np.nan, np.nan],
+                    [np.nan, np.nan],
+                    [2.0, np.nan],
+                    [np.nan, 2.0],
+                    [1.0, np.nan],
+                    [np.nan, 1.0],
+                ],
+            ),
+            (
+                False,
+                1,
+                [
+                    [np.nan, np.nan],
+                    [np.nan, np.nan],
+                    [1.0, np.nan],
+                    [0.5, 1.0],
+                    [np.nan, 0.5],
+                    [np.nan, np.nan],
+                    [np.nan, np.nan],
+                ],
+            ),
+            (
+                False,
+                2,
+                [
+                    [np.nan, np.nan],
+                    [np.nan, np.nan],
+                    [np.nan, np.nan],
+                    [2.0, np.nan],
+                    [np.nan, 2.0],
+                    [0.33333333, np.nan],
+                    [np.nan, 0.33333333],
+                ],
+            ),
+        ],
+    )
     def test_pct_change_skipna(self, skipna, periods, expected_vals):
         # GH25006
-        df = DataFrame([[np.nan, np.nan], [1., np.nan], [2., 1.], [3., 2.],
-                        [np.nan, 3.], [4., np.nan], [np.nan, 4.]])
+        df = DataFrame(
+            [
+                [np.nan, np.nan],
+                [1.0, np.nan],
+                [2.0, 1.0],
+                [3.0, 2.0],
+                [np.nan, 3.0],
+                [4.0, np.nan],
+                [np.nan, 4.0],
+            ]
+        )
         result = df.pct_change(skipna=skipna, periods=periods)
         expected = DataFrame(expected_vals)
         tm.assert_frame_equal(result, expected)
diff --git a/pandas/tests/frame/test_timeseries.py b/pandas/tests/frame/test_timeseries.py
index 716706e07ceb0..8c4ce7555526b 100644
--- a/pandas/tests/frame/test_timeseries.py
+++ b/pandas/tests/frame/test_timeseries.py
@@ -193,7 +193,9 @@ def test_pct_change_periods_freq(self, freq, periods, fill_method, limit):
 
         empty_ts = DataFrame(index=self.tsframe.index, columns=self.tsframe.columns)
         rs_freq = empty_ts.pct_change(freq=freq, fill_method=fill_method, limit=limit)
-        rs_periods = empty_ts.pct_change(periods=periods, fill_method=fill_method, limit=limit)
+        rs_periods = empty_ts.pct_change(
+            periods=periods, fill_method=fill_method, limit=limit
+        )
         assert_frame_equal(rs_freq, rs_periods)
 
     def test_frame_ctor_datetime64_column(self):
diff --git a/pandas/tests/generic/test_generic.py b/pandas/tests/generic/test_generic.py
index 0b43fd4468e4b..d60b706091d96 100644
--- a/pandas/tests/generic/test_generic.py
+++ b/pandas/tests/generic/test_generic.py
@@ -585,13 +585,16 @@ def test_pct_change(self, periods, fill_method, limit, exp):
         else:
             tm.assert_series_equal(res, Series(exp))
 
-    @pytest.mark.parametrize('fill_method, limit', [
-        ('backfill', None),
-        ('bfill', None),
-        ('pad', None),
-        ('ffill', None),
-        (None, 1)
-    ])
+    @pytest.mark.parametrize(
+        "fill_method, limit",
+        [
+            ("backfill", None),
+            ("bfill", None),
+            ("pad", None),
+            ("ffill", None),
+            (None, 1),
+        ],
+    )
     def test_pct_change_skipna_raises(self, fill_method, limit):
         # GH25006
         vals = [np.nan, np.nan, 1, 2, np.nan, 4, 10, np.nan]
@@ -601,8 +604,7 @@ def test_pct_change_skipna_raises(self, fill_method, limit):
         else:
             msg = "cannot pass both limit and skipna"
         with pytest.raises(ValueError, match=msg):
-            obj.pct_change(skipna=True, fill_method=fill_method,
-                           limit=limit)
+            obj.pct_change(skipna=True, fill_method=fill_method, limit=limit)
 
 
 class TestNDFrame:
diff --git a/pandas/tests/series/test_analytics.py b/pandas/tests/series/test_analytics.py
index f3d1ffa7cbd4d..a98c54401aef5 100644
--- a/pandas/tests/series/test_analytics.py
+++ b/pandas/tests/series/test_analytics.py
@@ -227,13 +227,16 @@ def test_cummax_timedelta64(self):
         result = s.cummax(skipna=False)
         tm.assert_series_equal(expected, result)
 
-    @pytest.mark.parametrize("periods, expected_vals", [
-        (1, [np.nan, np.nan, 1.0, 0.5, np.nan, 0.333333333333333, np.nan]),
-        (2, [np.nan, np.nan, np.nan, 2.0, np.nan, 1.0, np.nan])
-    ])
+    @pytest.mark.parametrize(
+        "periods, expected_vals",
+        [
+            (1, [np.nan, np.nan, 1.0, 0.5, np.nan, 0.333333333333333, np.nan]),
+            (2, [np.nan, np.nan, np.nan, 2.0, np.nan, 1.0, np.nan]),
+        ],
+    )
     def test_pct_change_skipna(self, periods, expected_vals):
         # GH25006
-        vals = [np.nan, 1., 2., 3., np.nan, 4., np.nan]
+        vals = [np.nan, 1.0, 2.0, 3.0, np.nan, 4.0, np.nan]
         s = Series(vals)
         result = s.pct_change(skipna=True, periods=periods)
         expected = Series(expected_vals)
@@ -1027,7 +1030,9 @@ def test_unstack(self):
         idx = pd.MultiIndex.from_arrays([[101, 102], [3.5, np.nan]])
         ts = pd.Series([1, 2], index=idx)
         left = ts.unstack()
-        right = DataFrame([[np.nan, 1], [2, np.nan]], index=[101, 102], columns=[np.nan, 3.5])
+        right = DataFrame(
+            [[np.nan, 1], [2, np.nan]], index=[101, 102], columns=[np.nan, 3.5]
+        )
         assert_frame_equal(left, right)
 
         idx = pd.MultiIndex.from_arrays(
@@ -1039,7 +1044,8 @@ def test_unstack(self):
         )
         ts = pd.Series([1.0, 1.1, 1.2, 1.3, 1.4], index=idx)
         right = DataFrame(
-            [[1.0, 1.3], [1.1, np.nan], [np.nan, 1.4], [1.2, np.nan]], columns=["cat", "dog"]
+            [[1.0, 1.3], [1.1, np.nan], [np.nan, 1.4], [1.2, np.nan]],
+            columns=["cat", "dog"],
         )
         tpls = [("a", 1), ("a", 2), ("b", np.nan), ("b", 1)]
         right.index = pd.MultiIndex.from_tuples(tpls)
diff --git a/pandas/tests/series/test_timeseries.py b/pandas/tests/series/test_timeseries.py
index bcadfa795b199..f353c672b6315 100644
--- a/pandas/tests/series/test_timeseries.py
+++ b/pandas/tests/series/test_timeseries.py
@@ -436,12 +436,16 @@ def test_pct_change_shift_over_nas(self):
     def test_pct_change_periods_freq(self, freq, periods, fill_method, limit):
         # GH 7292
         rs_freq = self.ts.pct_change(freq=freq, fill_method=fill_method, limit=limit)
-        rs_periods = self.ts.pct_change(periods=periods, fill_method=fill_method, limit=limit)
+        rs_periods = self.ts.pct_change(
+            periods=periods, fill_method=fill_method, limit=limit
+        )
         assert_series_equal(rs_freq, rs_periods)
 
         empty_ts = Series(index=self.ts.index)
         rs_freq = empty_ts.pct_change(freq=freq, fill_method=fill_method, limit=limit)
-        rs_periods = empty_ts.pct_change(periods=periods, fill_method=fill_method, limit=limit)
+        rs_periods = empty_ts.pct_change(
+            periods=periods, fill_method=fill_method, limit=limit
+        )
         assert_series_equal(rs_freq, rs_periods)
 
     def test_autocorr(self):

From 764846dc6c8925d83665905dc135a9c49cad2295 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Sun, 25 Aug 2019 19:41:26 -0700
Subject: [PATCH 19/23] Changed whatsnew

---
 doc/source/whatsnew/v0.25.0.rst | 1 -
 doc/source/whatsnew/v1.0.0.rst  | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/doc/source/whatsnew/v0.25.0.rst b/doc/source/whatsnew/v0.25.0.rst
index 22e2a768ad4c2..fe1e2d7826d62 100644
--- a/doc/source/whatsnew/v0.25.0.rst
+++ b/doc/source/whatsnew/v0.25.0.rst
@@ -876,7 +876,6 @@ Other API changes
 - :class:`DatetimeTZDtype` will now standardize pytz timezones to a common timezone instance (:issue:`24713`)
 - :class:`Timestamp` and :class:`Timedelta` scalars now implement the :meth:`to_numpy` method as aliases to :meth:`Timestamp.to_datetime64` and :meth:`Timedelta.to_timedelta64`, respectively. (:issue:`24653`)
 - :meth:`Timestamp.strptime` will now rise a ``NotImplementedError`` (:issue:`25016`)
-- Default `skipna=True` for :meth:`Series.pct_change` and :meth:`DataFrame.pct_change` will drop NAs before calculation (:issue:`25006`)
 - Comparing :class:`Timestamp` with unsupported objects now returns :py:obj:`NotImplemented` instead of raising ``TypeError``. This implies that unsupported rich comparisons are delegated to the other object, and are now consistent with Python 3 behavior for ``datetime`` objects (:issue:`24011`)
 - Bug in :meth:`DatetimeIndex.snap` which didn't preserving the ``name`` of the input :class:`Index` (:issue:`25575`)
 - The ``arg`` argument in :meth:`pandas.core.groupby.DataFrameGroupBy.agg` has been renamed to ``func`` (:issue:`26089`)
diff --git a/doc/source/whatsnew/v1.0.0.rst b/doc/source/whatsnew/v1.0.0.rst
index 8e25857e5ad69..df955ef3deb6f 100644
--- a/doc/source/whatsnew/v1.0.0.rst
+++ b/doc/source/whatsnew/v1.0.0.rst
@@ -29,7 +29,7 @@ Enhancements
 Other enhancements
 ^^^^^^^^^^^^^^^^^^
 
--
+- :meth:`Series.pct_change` and :meth:`DataFrame.pct_change` now accept a ``skipna`` argument (:issue:`25006`)
 -
 
 .. _whatsnew_1000.api_breaking:

From 71846986b25b7d6117f02edcc59b270f66d43d9c Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Sun, 25 Aug 2019 19:43:01 -0700
Subject: [PATCH 20/23] Updated versionadded

---
 pandas/core/generic.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 85fc4c102e955..1b1dbc2ce4757 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -10273,7 +10273,7 @@ def _check_percentile(self, q):
         skipna : bool, default True
             Exclude NA/null values before computing percent change.
 
-            .. versionadded:: 0.25.0
+            .. versionadded:: 1.0.0
         **kwargs
             Additional keyword arguments are passed into
             `DataFrame.shift` or `Series.shift`.

From 3821857f37492e8e881f390a46854231bf5bbef1 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 26 Aug 2019 16:07:37 -0700
Subject: [PATCH 21/23] Signature fixup

---
 pandas/core/generic.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 1b1dbc2ce4757..c51315343a64f 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -10445,7 +10445,9 @@ def _check_percentile(self, q):
         """
 
     @Appender(_shared_docs["pct_change"] % _shared_doc_kwargs)
-    def pct_change(self, periods=1, fill_method="pad", limit=None, freq=None, **kwargs):
+    def pct_change(
+        self, periods=1, fill_method="pad", limit=None, freq=None, skipna=None, **kwargs
+    ):
         if fill_method is not None and skipna:
             raise ValueError("cannot pass both fill_method and skipna")
         elif limit is not None and skipna:

From a2be8f6c681a2ae304a2b908346b8eb58d854812 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Wed, 28 Aug 2019 09:33:45 -0700
Subject: [PATCH 22/23] test failure fixup

---
 pandas/core/generic.py                | 2 +-
 pandas/tests/series/test_analytics.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index c51315343a64f..3786bdd7fd9ef 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -10446,7 +10446,7 @@ def _check_percentile(self, q):
 
     @Appender(_shared_docs["pct_change"] % _shared_doc_kwargs)
     def pct_change(
-        self, periods=1, fill_method="pad", limit=None, freq=None, skipna=None, **kwargs
+        self, periods=1, fill_method=None, limit=None, freq=None, skipna=None, **kwargs
     ):
         if fill_method is not None and skipna:
             raise ValueError("cannot pass both fill_method and skipna")
diff --git a/pandas/tests/series/test_analytics.py b/pandas/tests/series/test_analytics.py
index a98c54401aef5..65589b6402c60 100644
--- a/pandas/tests/series/test_analytics.py
+++ b/pandas/tests/series/test_analytics.py
@@ -490,7 +490,7 @@ def test_count(self, datetime_series):
 
         assert datetime_series.count() == np.isfinite(datetime_series).sum()
 
-        mi = MultiIndex.from_arrays([list("aabbcc"), [1, 2, 2, nan, 1, 2]])
+        mi = MultiIndex.from_arrays([list("aabbcc"), [1, 2, 2, np.nan, 1, 2]])
         ts = Series(np.arange(len(mi)), index=mi)
 
         left = ts.count(level=1)

From fd18d04772ad4a75b2df63470a2ffac619c9ff52 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Fri, 30 Aug 2019 10:35:41 -0600
Subject: [PATCH 23/23] docstring for skipna=False

---
 pandas/core/generic.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 897813daec943..117d9d9a27a58 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -10365,6 +10365,17 @@ def _check_percentile(self, q):
         5    0.117647
         dtype: float64
 
+        By contrast, `skipna=False` will not drop NA values before
+        computation, instead evaluating each entry against the entry prior.
+
+        >>> s.pct_change(skipna=False)
+        0         NaN
+        1    0.011111
+        2         NaN
+        3         NaN
+        4         NaN
+        5         NaN
+
         On the other hand, if a fill method is passed, NAs are filled before
         the computation. For example, before the computation of percentage
         change, forward fill method `ffill` first fills NAs with last valid