diff --git a/pandas/core/window.py b/pandas/core/window.py
index f7a60527602a1b..494ab5d5963ee5 100644
--- a/pandas/core/window.py
+++ b/pandas/core/window.py
@@ -7,41 +7,29 @@
 """
 from __future__ import division
 
-import warnings
-import numpy as np
 from collections import defaultdict
 from datetime import timedelta
+from textwrap import dedent
+import warnings
+
+import numpy as np
+
+import pandas._libs.window as libwindow
+import pandas.compat as compat
+from pandas.compat.numpy import function as nv
+from pandas.util._decorators import Appender, Substitution, cache_readonly
 
-from pandas.core.dtypes.generic import (
-    ABCSeries,
-    ABCDataFrame,
-    ABCDatetimeIndex,
-    ABCTimedeltaIndex,
-    ABCPeriodIndex,
-    ABCDateOffset)
 from pandas.core.dtypes.common import (
-    is_integer,
-    is_bool,
-    is_float_dtype,
-    is_integer_dtype,
-    needs_i8_conversion,
-    is_timedelta64_dtype,
-    is_list_like,
-    ensure_float64,
-    is_scalar)
+    ensure_float64, is_bool, is_float_dtype, is_integer, is_integer_dtype,
+    is_list_like, is_scalar, is_timedelta64_dtype, needs_i8_conversion)
+from pandas.core.dtypes.generic import (
+    ABCDataFrame, ABCDateOffset, ABCDatetimeIndex, ABCPeriodIndex, ABCSeries,
+    ABCTimedeltaIndex)
 
 from pandas.core.base import PandasObject, SelectionMixin
-from pandas.core.groupby.base import GroupByMixin
 import pandas.core.common as com
-import pandas._libs.window as _window
-
-from pandas import compat
-from pandas.compat.numpy import function as nv
-from pandas.util._decorators import (Substitution, Appender,
-                                     cache_readonly)
 from pandas.core.generic import _shared_docs
-from textwrap import dedent
-
+from pandas.core.groupby.base import GroupByMixin
 
 _shared_docs = dict(**_shared_docs)
 _doc_template = """
@@ -688,10 +676,10 @@ def _apply_window(self, mean=True, **kwargs):
 
             def f(arg, *args, **kwargs):
                 minp = _use_window(self.min_periods, len(window))
-                return _window.roll_window(np.concatenate((arg,
-                                                           additional_nans))
-                                           if center else arg, window, minp,
-                                           avg=mean)
+                return libwindow.roll_window(np.concatenate((arg,
+                                                             additional_nans))
+                                             if center else arg, window, minp,
+                                             avg=mean)
 
             result = np.apply_along_axis(f, self.axis, values)
 
@@ -848,10 +836,10 @@ def _apply(self, func, name=None, window=None, center=None,
 
             # if we have a string function name, wrap it
             if isinstance(func, compat.string_types):
-                cfunc = getattr(_window, func, None)
+                cfunc = getattr(libwindow, func, None)
                 if cfunc is None:
                     raise ValueError("we do not support this function "
-                                     "in _window.{0}".format(func))
+                                     "in libwindow.{func}".format(func=func))
 
                 def func(arg, window, min_periods=None, closed=None):
                     minp = check_minp(min_periods, window)
@@ -995,7 +983,7 @@ def f(arg, window, min_periods, closed):
             minp = _use_window(min_periods, window)
             if not raw:
                 arg = Series(arg, index=self.obj.index)
-            return _window.roll_generic(
+            return libwindow.roll_generic(
                 arg, window, minp, indexi,
                 closed, offset, func, raw, args, kwargs)
 
@@ -1160,8 +1148,8 @@ def std(self, ddof=1, *args, **kwargs):
 
         def f(arg, *args, **kwargs):
             minp = _require_min_periods(1)(self.min_periods, window)
-            return _zsqrt(_window.roll_var(arg, window, minp, indexi,
-                                           self.closed, ddof))
+            return _zsqrt(libwindow.roll_var(arg, window, minp, indexi,
+                                             self.closed, ddof))
 
         return self._apply(f, 'std', check_minp=_require_min_periods(1),
                            ddof=ddof, **kwargs)
@@ -1331,15 +1319,15 @@ def quantile(self, quantile, interpolation='linear', **kwargs):
         def f(arg, *args, **kwargs):
             minp = _use_window(self.min_periods, window)
             if quantile == 1.0:
-                return _window.roll_max(arg, window, minp, indexi,
-                                        self.closed)
+                return libwindow.roll_max(arg, window, minp, indexi,
+                                          self.closed)
             elif quantile == 0.0:
-                return _window.roll_min(arg, window, minp, indexi,
-                                        self.closed)
+                return libwindow.roll_min(arg, window, minp, indexi,
+                                          self.closed)
             else:
-                return _window.roll_quantile(arg, window, minp, indexi,
-                                             self.closed, quantile,
-                                             interpolation)
+                return libwindow.roll_quantile(arg, window, minp, indexi,
+                                               self.closed, quantile,
+                                               interpolation)
 
         return self._apply(f, 'quantile', quantile=quantile,
                            **kwargs)
@@ -2262,10 +2250,10 @@ def _apply(self, func, **kwargs):
 
             # if we have a string function name, wrap it
             if isinstance(func, compat.string_types):
-                cfunc = getattr(_window, func, None)
+                cfunc = getattr(libwindow, func, None)
                 if cfunc is None:
                     raise ValueError("we do not support this function "
-                                     "in _window.{0}".format(func))
+                                     "in libwindow.{func}".format(func=func))
 
                 def func(arg):
                     return cfunc(arg, self.com, int(self.adjust),
@@ -2300,9 +2288,9 @@ def var(self, bias=False, *args, **kwargs):
         nv.validate_window_func('var', args, kwargs)
 
         def f(arg):
-            return _window.ewmcov(arg, arg, self.com, int(self.adjust),
-                                  int(self.ignore_na), int(self.min_periods),
-                                  int(bias))
+            return libwindow.ewmcov(arg, arg, self.com, int(self.adjust),
+                                    int(self.ignore_na), int(self.min_periods),
+                                    int(bias))
 
         return self._apply(f, **kwargs)
 
@@ -2320,9 +2308,10 @@ def cov(self, other=None, pairwise=None, bias=False, **kwargs):
         def _get_cov(X, Y):
             X = self._shallow_copy(X)
             Y = self._shallow_copy(Y)
-            cov = _window.ewmcov(X._prep_values(), Y._prep_values(), self.com,
-                                 int(self.adjust), int(self.ignore_na),
-                                 int(self.min_periods), int(bias))
+            cov = libwindow.ewmcov(X._prep_values(), Y._prep_values(),
+                                   self.com, int(self.adjust),
+                                   int(self.ignore_na), int(self.min_periods),
+                                   int(bias))
             return X._wrap_result(cov)
 
         return _flex_binary_moment(self._selected_obj, other._selected_obj,
@@ -2344,10 +2333,10 @@ def _get_corr(X, Y):
             Y = self._shallow_copy(Y)
 
             def _cov(x, y):
-                return _window.ewmcov(x, y, self.com, int(self.adjust),
-                                      int(self.ignore_na),
-                                      int(self.min_periods),
-                                      1)
+                return libwindow.ewmcov(x, y, self.com, int(self.adjust),
+                                        int(self.ignore_na),
+                                        int(self.min_periods),
+                                        1)
 
             x_values = X._prep_values()
             y_values = Y._prep_values()
diff --git a/pandas/tests/scalar/interval/test_interval.py b/pandas/tests/scalar/interval/test_interval.py
index 7951fb7ddda0d6..432f44725e2ba0 100644
--- a/pandas/tests/scalar/interval/test_interval.py
+++ b/pandas/tests/scalar/interval/test_interval.py
@@ -1,11 +1,11 @@
 from __future__ import division
 
 import numpy as np
-from pandas import Interval, Timestamp, Timedelta
-import pandas.core.common as com
-
 import pytest
 
+from pandas import Interval, Timedelta, Timestamp
+import pandas.core.common as com
+
 
 @pytest.fixture
 def interval():
diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 23762fda8c22af..064d1a96878c22 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -1,11 +1,11 @@
 import pytest
 
+from pandas._libs.tslibs.frequencies import (
+    INVALID_FREQ_ERR_MSG, _period_code_map)
 from pandas.errors import OutOfBoundsDatetime
 
-import pandas as pd
 from pandas import Period, offsets
 from pandas.util import testing as tm
-from pandas._libs.tslibs.frequencies import _period_code_map
 
 
 class TestFreqConversion(object):
@@ -328,13 +328,13 @@ def test_conv_weekly(self):
 
         assert ival_W.asfreq('W') == ival_W
 
-        msg = pd._libs.tslibs.frequencies.INVALID_FREQ_ERR_MSG
+        msg = INVALID_FREQ_ERR_MSG
         with pytest.raises(ValueError, match=msg):
             ival_W.asfreq('WK')
 
     def test_conv_weekly_legacy(self):
         # frequency conversion tests: from Weekly Frequency
-        msg = pd._libs.tslibs.frequencies.INVALID_FREQ_ERR_MSG
+        msg = INVALID_FREQ_ERR_MSG
         with pytest.raises(ValueError, match=msg):
             Period(freq='WK', year=2007, month=1, day=1)
 
@@ -741,11 +741,11 @@ def test_asfreq_MS(self):
 
         assert initial.asfreq(freq="M", how="S") == Period('2013-01', 'M')
 
-        msg = pd._libs.tslibs.frequencies.INVALID_FREQ_ERR_MSG
+        msg = INVALID_FREQ_ERR_MSG
         with pytest.raises(ValueError, match=msg):
             initial.asfreq(freq="MS", how="S")
 
         with pytest.raises(ValueError, match=msg):
-            pd.Period('2013-01', 'MS')
+            Period('2013-01', 'MS')
 
         assert _period_code_map.get("MS") is None
diff --git a/pandas/tests/scalar/period/test_period.py b/pandas/tests/scalar/period/test_period.py
index 14b26bce42d87d..4d3aa1109c1208 100644
--- a/pandas/tests/scalar/period/test_period.py
+++ b/pandas/tests/scalar/period/test_period.py
@@ -1,20 +1,21 @@
-import pytest
+from datetime import date, datetime, timedelta
 
-import pytz
 import numpy as np
-from datetime import datetime, date, timedelta
-
-import pandas as pd
-from pandas import Timedelta, NaT, Period, Timestamp, offsets
-import pandas.util.testing as tm
-import pandas.core.indexes.period as period
-from pandas.compat import text_type, iteritems
-from pandas.compat.numpy import np_datetime64_compat
+import pytest
+import pytz
 
 from pandas._libs.tslibs import iNaT, period as libperiod
 from pandas._libs.tslibs.ccalendar import DAYS, MONTHS
+from pandas._libs.tslibs.frequencies import INVALID_FREQ_ERR_MSG
 from pandas._libs.tslibs.parsing import DateParseError
 from pandas._libs.tslibs.timezones import dateutil_gettz, maybe_get_tz
+from pandas.compat import iteritems, text_type
+from pandas.compat.numpy import np_datetime64_compat
+
+import pandas as pd
+from pandas import NaT, Period, Timedelta, Timestamp, offsets
+import pandas.core.indexes.period as period
+import pandas.util.testing as tm
 
 
 class TestPeriodConstruction(object):
@@ -712,7 +713,7 @@ def test_period_deprecated_freq(self):
                  "U": ["MICROSECOND", "MICROSECONDLY", "microsecond"],
                  "N": ["NANOSECOND", "NANOSECONDLY", "nanosecond"]}
 
-        msg = pd._libs.tslibs.frequencies.INVALID_FREQ_ERR_MSG
+        msg = INVALID_FREQ_ERR_MSG
         for exp, freqs in iteritems(cases):
             for freq in freqs:
                 with pytest.raises(ValueError, match=msg):
@@ -851,7 +852,7 @@ def test_properties_weekly_legacy(self):
         exp = Period(freq='W', year=2012, month=2, day=1)
         assert exp.days_in_month == 29
 
-        msg = pd._libs.tslibs.frequencies.INVALID_FREQ_ERR_MSG
+        msg = INVALID_FREQ_ERR_MSG
         with pytest.raises(ValueError, match=msg):
             Period(freq='WK', year=2007, month=1, day=7)
 
diff --git a/pandas/tests/scalar/test_nat.py b/pandas/tests/scalar/test_nat.py
index b49da5ed4eb24d..ddf39847441146 100644
--- a/pandas/tests/scalar/test_nat.py
+++ b/pandas/tests/scalar/test_nat.py
@@ -1,15 +1,16 @@
-import pytest
-
 from datetime import datetime, timedelta
-import pytz
 
 import numpy as np
-from pandas import (NaT, Index, Timestamp, Timedelta, Period,
-                    DatetimeIndex,
-                    TimedeltaIndex, Series, isna)
+import pytest
+import pytz
+
+from pandas._libs.tslib import iNaT
+
+from pandas import (
+    DatetimeIndex, Index, NaT, Period, Series, Timedelta, TimedeltaIndex,
+    Timestamp, isna)
 from pandas.core.arrays import PeriodArray
 from pandas.util import testing as tm
-from pandas._libs.tslib import iNaT
 
 
 @pytest.mark.parametrize('nat, idx', [(Timestamp('NaT'), DatetimeIndex),
diff --git a/pandas/tests/scalar/timedelta/test_arithmetic.py b/pandas/tests/scalar/timedelta/test_arithmetic.py
index b9af31db1d6e6c..b6ad251d598ab7 100644
--- a/pandas/tests/scalar/timedelta/test_arithmetic.py
+++ b/pandas/tests/scalar/timedelta/test_arithmetic.py
@@ -9,9 +9,9 @@
 import pytest
 
 import pandas as pd
-import pandas.util.testing as tm
+from pandas import NaT, Timedelta, Timestamp
 from pandas.core import ops
-from pandas import Timedelta, Timestamp, NaT
+import pandas.util.testing as tm
 
 
 class TestTimedeltaAdditionSubtraction(object):
@@ -189,54 +189,54 @@ def test_td_rsub_offset(self):
         assert result == Timedelta(-239, unit='h')
 
     def test_td_sub_timedeltalike_object_dtype_array(self):
-        # GH 21980
+        # GH#21980
         arr = np.array([Timestamp('20130101 9:01'),
                         Timestamp('20121230 9:02')])
         exp = np.array([Timestamp('20121231 9:01'),
                         Timestamp('20121229 9:02')])
-        res = arr - pd.Timedelta('1D')
+        res = arr - Timedelta('1D')
         tm.assert_numpy_array_equal(res, exp)
 
     def test_td_sub_mixed_most_timedeltalike_object_dtype_array(self):
-        # GH 21980
-        now = pd.Timestamp.now()
+        # GH#21980
+        now = Timestamp.now()
         arr = np.array([now,
-                        pd.Timedelta('1D'),
+                        Timedelta('1D'),
                         np.timedelta64(2, 'h')])
-        exp = np.array([now - pd.Timedelta('1D'),
-                        pd.Timedelta('0D'),
-                        np.timedelta64(2, 'h') - pd.Timedelta('1D')])
-        res = arr - pd.Timedelta('1D')
+        exp = np.array([now - Timedelta('1D'),
+                        Timedelta('0D'),
+                        np.timedelta64(2, 'h') - Timedelta('1D')])
+        res = arr - Timedelta('1D')
         tm.assert_numpy_array_equal(res, exp)
 
     def test_td_rsub_mixed_most_timedeltalike_object_dtype_array(self):
-        # GH 21980
-        now = pd.Timestamp.now()
+        # GH#21980
+        now = Timestamp.now()
         arr = np.array([now,
-                        pd.Timedelta('1D'),
+                        Timedelta('1D'),
                         np.timedelta64(2, 'h')])
         with pytest.raises(TypeError):
-            pd.Timedelta('1D') - arr
+            Timedelta('1D') - arr
 
     @pytest.mark.parametrize('op', [operator.add, ops.radd])
     def test_td_add_timedeltalike_object_dtype_array(self, op):
-        # GH 21980
+        # GH#21980
         arr = np.array([Timestamp('20130101 9:01'),
                         Timestamp('20121230 9:02')])
         exp = np.array([Timestamp('20130102 9:01'),
                         Timestamp('20121231 9:02')])
-        res = op(arr, pd.Timedelta('1D'))
+        res = op(arr, Timedelta('1D'))
         tm.assert_numpy_array_equal(res, exp)
 
     @pytest.mark.parametrize('op', [operator.add, ops.radd])
     def test_td_add_mixed_timedeltalike_object_dtype_array(self, op):
-        # GH 21980
-        now = pd.Timestamp.now()
+        # GH#21980
+        now = Timestamp.now()
         arr = np.array([now,
-                        pd.Timedelta('1D')])
-        exp = np.array([now + pd.Timedelta('1D'),
-                        pd.Timedelta('2D')])
-        res = op(arr, pd.Timedelta('1D'))
+                        Timedelta('1D')])
+        exp = np.array([now + Timedelta('1D'),
+                        Timedelta('2D')])
+        res = op(arr, Timedelta('1D'))
         tm.assert_numpy_array_equal(res, exp)
 
 
@@ -255,7 +255,7 @@ class TestTimedeltaMultiplicationDivision(object):
     # ---------------------------------------------------------------
     # Timedelta.__mul__, __rmul__
 
-    @pytest.mark.parametrize('td_nat', [pd.NaT,
+    @pytest.mark.parametrize('td_nat', [NaT,
                                         np.timedelta64('NaT', 'ns'),
                                         np.timedelta64('NaT')])
     @pytest.mark.parametrize('op', [operator.mul, ops.rmul])
@@ -558,7 +558,7 @@ def test_mod_invalid(self):
         td = Timedelta(hours=37)
 
         with pytest.raises(TypeError):
-            td % pd.Timestamp('2018-01-22')
+            td % Timestamp('2018-01-22')
 
         with pytest.raises(TypeError):
             td % []
@@ -583,7 +583,7 @@ def test_rmod_invalid(self):
         td = Timedelta(minutes=3)
 
         with pytest.raises(TypeError):
-            pd.Timestamp('2018-01-22') % td
+            Timestamp('2018-01-22') % td
 
         with pytest.raises(TypeError):
             15 % td
@@ -608,8 +608,8 @@ def test_divmod_numeric(self):
 
         assert result
         result = divmod(td, np.nan)
-        assert result[0] is pd.NaT
-        assert result[1] is pd.NaT
+        assert result[0] is NaT
+        assert result[1] is NaT
 
     def test_divmod(self):
         # GH#19365
@@ -625,9 +625,9 @@ def test_divmod(self):
         assert isinstance(result[1], Timedelta)
         assert result[1] == Timedelta(0)
 
-        result = divmod(td, pd.NaT)
+        result = divmod(td, NaT)
         assert np.isnan(result[0])
-        assert result[1] is pd.NaT
+        assert result[1] is NaT
 
     def test_divmod_offset(self):
         # GH#19365
@@ -643,7 +643,7 @@ def test_divmod_invalid(self):
         td = Timedelta(days=2, hours=6)
 
         with pytest.raises(TypeError):
-            divmod(td, pd.Timestamp('2018-01-22'))
+            divmod(td, Timestamp('2018-01-22'))
 
     def test_rdivmod_pytimedelta(self):
         # GH#19365
@@ -663,7 +663,7 @@ def test_rdivmod_invalid(self):
         td = Timedelta(minutes=3)
 
         with pytest.raises(TypeError):
-            divmod(pd.Timestamp('2018-01-22'), td)
+            divmod(Timestamp('2018-01-22'), td)
 
         with pytest.raises(TypeError):
             divmod(15, td)
@@ -684,8 +684,8 @@ def test_rdivmod_invalid(self):
         ops.rsub])
     @pytest.mark.parametrize('arr', [
         np.array([Timestamp('20130101 9:01'), Timestamp('20121230 9:02')]),
-        np.array([pd.Timestamp.now(), pd.Timedelta('1D')])
+        np.array([Timestamp.now(), Timedelta('1D')])
     ])
     def test_td_op_timedelta_timedeltalike_array(self, op, arr):
         with pytest.raises(TypeError):
-            op(arr, pd.Timedelta('1D'))
+            op(arr, Timedelta('1D'))
diff --git a/pandas/tests/scalar/timedelta/test_construction.py b/pandas/tests/scalar/timedelta/test_construction.py
index 4165b1aec705f2..880eca914749b7 100644
--- a/pandas/tests/scalar/timedelta/test_construction.py
+++ b/pandas/tests/scalar/timedelta/test_construction.py
@@ -1,11 +1,10 @@
 # -*- coding: utf-8 -*-
 from datetime import timedelta
 
-import pytest
 import numpy as np
+import pytest
 
-import pandas as pd
-from pandas import Timedelta
+from pandas import Timedelta, offsets, to_timedelta
 
 
 def test_construction():
@@ -107,16 +106,15 @@ def test_construction():
     assert Timedelta(10.5, unit='s').value == expected
 
     # offset
-    assert pd.to_timedelta(pd.offsets.Hour(2)) == Timedelta(hours=2)
-    assert Timedelta(pd.offsets.Hour(2)) == Timedelta(hours=2)
-    assert Timedelta(pd.offsets.Second(2)) == Timedelta(seconds=2)
+    assert to_timedelta(offsets.Hour(2)) == Timedelta(hours=2)
+    assert Timedelta(offsets.Hour(2)) == Timedelta(hours=2)
+    assert Timedelta(offsets.Second(2)) == Timedelta(seconds=2)
 
     # GH#11995: unicode
     expected = Timedelta('1H')
-    result = pd.Timedelta(u'1H')
+    result = Timedelta(u'1H')
     assert result == expected
-    assert (pd.to_timedelta(pd.offsets.Hour(2)) ==
-            Timedelta(u'0 days, 02:00:00'))
+    assert to_timedelta(offsets.Hour(2)) == Timedelta(u'0 days, 02:00:00')
 
     with pytest.raises(ValueError):
         Timedelta(u'foo bar')
@@ -154,17 +152,17 @@ def test_td_from_repr_roundtrip(val):
 
 
 def test_overflow_on_construction():
-    # xref https://github.com/statsmodels/statsmodels/issues/3374
-    value = pd.Timedelta('1day').value * 20169940
+    # GH#3374
+    value = Timedelta('1day').value * 20169940
     with pytest.raises(OverflowError):
-        pd.Timedelta(value)
+        Timedelta(value)
 
     # xref GH#17637
     with pytest.raises(OverflowError):
-        pd.Timedelta(7 * 19999, unit='D')
+        Timedelta(7 * 19999, unit='D')
 
     with pytest.raises(OverflowError):
-        pd.Timedelta(timedelta(days=13 * 19999))
+        Timedelta(timedelta(days=13 * 19999))
 
 
 @pytest.mark.parametrize('fmt,exp', [
diff --git a/pandas/tests/scalar/timedelta/test_timedelta.py b/pandas/tests/scalar/timedelta/test_timedelta.py
index 58064213d9b3b7..f7dac81a5b8d71 100644
--- a/pandas/tests/scalar/timedelta/test_timedelta.py
+++ b/pandas/tests/scalar/timedelta/test_timedelta.py
@@ -1,15 +1,17 @@
 """ test the scalar Timedelta """
-import pytest
+from datetime import timedelta
 
 import numpy as np
-from datetime import timedelta
+import pytest
+
+from pandas._libs.tslib import NaT, iNaT
+import pandas.compat as compat
 
 import pandas as pd
-import pandas.util.testing as tm
+from pandas import (
+    Series, Timedelta, TimedeltaIndex, timedelta_range, to_timedelta)
 from pandas.core.tools.timedeltas import _coerce_scalar_to_timedelta_type as ct
-from pandas import (Timedelta, TimedeltaIndex, timedelta_range, Series,
-                    to_timedelta, compat)
-from pandas._libs.tslib import iNaT, NaT
+import pandas.util.testing as tm
 
 
 class TestTimedeltaArithmetic(object):
diff --git a/pandas/tests/scalar/timestamp/test_arithmetic.py b/pandas/tests/scalar/timestamp/test_arithmetic.py
index 207bd103105ea8..331d66589802dd 100644
--- a/pandas/tests/scalar/timestamp/test_arithmetic.py
+++ b/pandas/tests/scalar/timestamp/test_arithmetic.py
@@ -1,14 +1,16 @@
 # -*- coding: utf-8 -*-
 from datetime import datetime, timedelta
 
-import pytest
 import numpy as np
+import pytest
 
-import pandas.util.testing as tm
 from pandas.compat import long
+
+from pandas import Timedelta, Timestamp
+import pandas.util.testing as tm
+
 from pandas.tseries import offsets
 from pandas.tseries.frequencies import to_offset
-from pandas import Timestamp, Timedelta
 
 
 class TestTimestampArithmetic(object):
diff --git a/pandas/tests/scalar/timestamp/test_comparisons.py b/pandas/tests/scalar/timestamp/test_comparisons.py
index f293f8f161010a..74dd52c48153f2 100644
--- a/pandas/tests/scalar/timestamp/test_comparisons.py
+++ b/pandas/tests/scalar/timestamp/test_comparisons.py
@@ -2,10 +2,11 @@
 from datetime import datetime
 import operator
 
-import pytest
 import numpy as np
+import pytest
+
+from pandas.compat import PY2, long
 
-from pandas.compat import long, PY2
 from pandas import Timestamp
 
 
diff --git a/pandas/tests/scalar/timestamp/test_rendering.py b/pandas/tests/scalar/timestamp/test_rendering.py
index c404b60567daf4..29b65ee4df745e 100644
--- a/pandas/tests/scalar/timestamp/test_rendering.py
+++ b/pandas/tests/scalar/timestamp/test_rendering.py
@@ -1,12 +1,12 @@
 # -*- coding: utf-8 -*-
 
-import pytest
+from distutils.version import LooseVersion
+import pprint
+
 import dateutil
+import pytest
 import pytz  # noqa  # a test below uses pytz but only inside a `eval` call
 
-import pprint
-from distutils.version import LooseVersion
-
 from pandas import Timestamp
 
 
diff --git a/pandas/tests/scalar/timestamp/test_timestamp.py b/pandas/tests/scalar/timestamp/test_timestamp.py
index c1f532d56304c5..2d5c8f77dd3380 100644
--- a/pandas/tests/scalar/timestamp/test_timestamp.py
+++ b/pandas/tests/scalar/timestamp/test_timestamp.py
@@ -1,29 +1,28 @@
 """ test the scalar Timestamp """
 
-import pytz
-import pytest
-import dateutil
 import calendar
+from datetime import datetime, timedelta
 import locale
 import unicodedata
-import numpy as np
 
+import dateutil
 from dateutil.tz import tzutc
+import numpy as np
+import pytest
+import pytz
 from pytz import timezone, utc
-from datetime import datetime, timedelta
 
-import pandas.util.testing as tm
+from pandas._libs.tslibs import conversion
+from pandas._libs.tslibs.timezones import dateutil_gettz as gettz, get_timezone
+from pandas.compat import PY2, PY3, long
+from pandas.compat.numpy import np_datetime64_compat
+from pandas.errors import OutOfBoundsDatetime
 import pandas.util._test_decorators as td
 
-from pandas.tseries import offsets
-
-from pandas._libs.tslibs import conversion
-from pandas._libs.tslibs.timezones import get_timezone, dateutil_gettz as gettz
+from pandas import NaT, Period, Timedelta, Timestamp
+import pandas.util.testing as tm
 
-from pandas.errors import OutOfBoundsDatetime
-from pandas.compat import long, PY3, PY2
-from pandas.compat.numpy import np_datetime64_compat
-from pandas import Timestamp, Period, Timedelta, NaT
+from pandas.tseries import offsets
 
 
 class TestTimestampProperties(object):
diff --git a/pandas/tests/scalar/timestamp/test_timezones.py b/pandas/tests/scalar/timestamp/test_timezones.py
index 6755d0bd4ae275..72e4fd42ae15a2 100644
--- a/pandas/tests/scalar/timestamp/test_timezones.py
+++ b/pandas/tests/scalar/timestamp/test_timezones.py
@@ -2,20 +2,20 @@
 """
 Tests for Timestamp timezone-related methods
 """
-from datetime import datetime, date, timedelta
-
+from datetime import date, datetime, timedelta
 from distutils.version import LooseVersion
+
+import dateutil
+from dateutil.tz import gettz, tzoffset
 import pytest
 import pytz
 from pytz.exceptions import AmbiguousTimeError, NonExistentTimeError
-import dateutil
-from dateutil.tz import gettz, tzoffset
 
-import pandas.util.testing as tm
+from pandas.errors import OutOfBoundsDatetime
 import pandas.util._test_decorators as td
 
-from pandas import Timestamp, NaT
-from pandas.errors import OutOfBoundsDatetime
+from pandas import NaT, Timestamp
+import pandas.util.testing as tm
 
 
 class TestTimestampTZOperations(object):
diff --git a/pandas/tests/scalar/timestamp/test_unary_ops.py b/pandas/tests/scalar/timestamp/test_unary_ops.py
index 21404bf7ef76fd..d3ca85df3fd4f0 100644
--- a/pandas/tests/scalar/timestamp/test_unary_ops.py
+++ b/pandas/tests/scalar/timestamp/test_unary_ops.py
@@ -1,18 +1,19 @@
 # -*- coding: utf-8 -*-
 from datetime import datetime
 
+from dateutil.tz import gettz
 import pytest
 import pytz
 from pytz import utc
-from dateutil.tz import gettz
-
-import pandas.util.testing as tm
-import pandas.util._test_decorators as td
 
-from pandas.compat import PY3
 from pandas._libs.tslibs import conversion
 from pandas._libs.tslibs.frequencies import INVALID_FREQ_ERR_MSG
-from pandas import Timestamp, NaT
+from pandas.compat import PY3
+import pandas.util._test_decorators as td
+
+from pandas import NaT, Timestamp
+import pandas.util.testing as tm
+
 from pandas.tseries.frequencies import to_offset
 
 
diff --git a/pandas/tests/tslibs/test_array_to_datetime.py b/pandas/tests/tslibs/test_array_to_datetime.py
index f2d9f35256a10a..ff8880257b2256 100644
--- a/pandas/tests/tslibs/test_array_to_datetime.py
+++ b/pandas/tests/tslibs/test_array_to_datetime.py
@@ -1,13 +1,14 @@
 # -*- coding: utf-8 -*-
-from datetime import datetime, date
+from datetime import date, datetime
 
+from dateutil.tz.tz import tzoffset
 import numpy as np
 import pytest
 import pytz
-from dateutil.tz.tz import tzoffset
 
 from pandas._libs import iNaT, tslib
 from pandas.compat.numpy import np_array_datetime64_compat
+
 import pandas.util.testing as tm
 
 
diff --git a/pandas/tests/tslibs/test_conversion.py b/pandas/tests/tslibs/test_conversion.py
index 76038136c26cb6..de36c0bb2f789a 100644
--- a/pandas/tests/tslibs/test_conversion.py
+++ b/pandas/tests/tslibs/test_conversion.py
@@ -3,11 +3,12 @@
 import numpy as np
 import pytest
 
-import pandas.util.testing as tm
-from pandas import date_range
 from pandas._libs.tslib import iNaT
 from pandas._libs.tslibs import conversion, timezones
 
+from pandas import date_range
+import pandas.util.testing as tm
+
 
 def compare_utc_to_local(tz_didx, utc_didx):
     f = lambda x: conversion.tz_convert_single(x, 'UTC', tz_didx.tz)
diff --git a/pandas/tests/tslibs/test_libfrequencies.py b/pandas/tests/tslibs/test_libfrequencies.py
index 18840fe1fd9b95..1bf6d0596e2fe9 100644
--- a/pandas/tests/tslibs/test_libfrequencies.py
+++ b/pandas/tests/tslibs/test_libfrequencies.py
@@ -2,11 +2,11 @@
 
 import pytest
 
+from pandas._libs.tslibs.frequencies import (
+    INVALID_FREQ_ERR_MSG, _period_str_to_code, get_rule_month, is_subperiod,
+    is_superperiod)
+
 from pandas.tseries import offsets
-from pandas._libs.tslibs.frequencies import (get_rule_month,
-                                             _period_str_to_code,
-                                             INVALID_FREQ_ERR_MSG,
-                                             is_superperiod, is_subperiod)
 
 
 def assert_aliases_deprecated(freq, expected, aliases):
diff --git a/pandas/tests/tslibs/test_parsing.py b/pandas/tests/tslibs/test_parsing.py
index 2762fb9cbe0000..f2b0ae98aff981 100644
--- a/pandas/tests/tslibs/test_parsing.py
+++ b/pandas/tests/tslibs/test_parsing.py
@@ -3,15 +3,17 @@
 Tests for Timestamp parsing, aimed at pandas/_libs/tslibs/parsing.pyx
 """
 from datetime import datetime
+
+from dateutil.parser import parse
 import numpy as np
 import pytest
-from dateutil.parser import parse
 
-import pandas.util._test_decorators as td
-from pandas import compat
-from pandas.util import testing as tm
 from pandas._libs.tslibs import parsing
 from pandas._libs.tslibs.parsing import parse_time_string
+import pandas.compat as compat
+import pandas.util._test_decorators as td
+
+from pandas.util import testing as tm
 
 
 class TestParseQuarters(object):
diff --git a/pandas/tests/tslibs/test_period_asfreq.py b/pandas/tests/tslibs/test_period_asfreq.py
index 61737083e22ead..e5978a59bc2a17 100644
--- a/pandas/tests/tslibs/test_period_asfreq.py
+++ b/pandas/tests/tslibs/test_period_asfreq.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 
 from pandas._libs.tslibs.frequencies import get_freq
-from pandas._libs.tslibs.period import period_ordinal, period_asfreq
+from pandas._libs.tslibs.period import period_asfreq, period_ordinal
 
 
 class TestPeriodFreqConversion(object):
diff --git a/pandas/tests/tslibs/test_timezones.py b/pandas/tests/tslibs/test_timezones.py
index 12f04505d953d6..68a6c1b09b9929 100644
--- a/pandas/tests/tslibs/test_timezones.py
+++ b/pandas/tests/tslibs/test_timezones.py
@@ -1,11 +1,12 @@
 # -*- coding: utf-8 -*-
 from datetime import datetime
 
+import dateutil.tz
 import pytest
 import pytz
-import dateutil.tz
 
-from pandas._libs.tslibs import timezones, conversion
+from pandas._libs.tslibs import conversion, timezones
+
 from pandas import Timestamp
 
 
diff --git a/pandas/tests/tslibs/test_tslib.py b/pandas/tests/tslibs/test_tslib.py
index 0df9328d0db160..17bd46cd235da5 100644
--- a/pandas/tests/tslibs/test_tslib.py
+++ b/pandas/tests/tslibs/test_tslib.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 """Tests for functions from pandas._libs.tslibs"""
 
-from datetime import datetime, date
+from datetime import date, datetime
 
 from pandas._libs import tslibs
 
diff --git a/pandas/tseries/converter.py b/pandas/tseries/converter.py
index 26d3f3cb85edcb..05dd7cea1bd2fb 100644
--- a/pandas/tseries/converter.py
+++ b/pandas/tseries/converter.py
@@ -1,15 +1,11 @@
 # flake8: noqa
 import warnings
 
-from pandas.plotting._converter import (time2num,
-                                        TimeConverter, TimeFormatter,
-                                        PeriodConverter, get_datevalue,
-                                        DatetimeConverter,
-                                        PandasAutoDateFormatter,
-                                        PandasAutoDateLocator,
-                                        MilliSecondLocator, get_finder,
-                                        TimeSeries_DateLocator,
-                                        TimeSeries_DateFormatter)
+from pandas.plotting._converter import (
+    DatetimeConverter, MilliSecondLocator, PandasAutoDateFormatter,
+    PandasAutoDateLocator, PeriodConverter, TimeConverter, TimeFormatter,
+    TimeSeries_DateFormatter, TimeSeries_DateLocator, get_datevalue,
+    get_finder, time2num)
 
 
 def register():
diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index ac9a87b2580564..95904fab053221 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -1,40 +1,37 @@
 # -*- coding: utf-8 -*-
 from datetime import timedelta
-from pandas.compat import zip
-from pandas import compat
 import re
 
 import numpy as np
+from pytz import AmbiguousTimeError
 
-from pandas.util._decorators import cache_readonly
-
-from pandas.core.dtypes.generic import ABCSeries
-from pandas.core.dtypes.common import (
-    is_period_arraylike,
-    is_timedelta64_dtype,
-    is_datetime64_dtype)
-
-from pandas.core.algorithms import unique
-
-from pandas.tseries.offsets import DateOffset
-
+from pandas._libs.algos import unique_deltas
 from pandas._libs.tslibs import Timedelta, Timestamp
-
+from pandas._libs.tslibs.ccalendar import MONTH_ALIASES, int_to_weekday
+from pandas._libs.tslibs.conversion import tz_convert
+from pandas._libs.tslibs.fields import build_field_sarray
 import pandas._libs.tslibs.frequencies as libfreqs
 from pandas._libs.tslibs.frequencies import (  # noqa, semi-public API
-    get_freq, get_base_alias, get_to_timestamp_base, get_freq_code,
-    FreqGroup,
+    FreqGroup, get_base_alias, get_freq, get_freq_code, get_to_timestamp_base,
     is_subperiod, is_superperiod)
-from pandas._libs.tslibs.ccalendar import MONTH_ALIASES, int_to_weekday
+from pandas._libs.tslibs.offsets import _offset_to_period_map  # noqa:E402
 import pandas._libs.tslibs.resolution as libresolution
 from pandas._libs.tslibs.resolution import Resolution
-from pandas._libs.tslibs.fields import build_field_sarray
-from pandas._libs.tslibs.conversion import tz_convert
+import pandas.compat as compat
+from pandas.compat import zip
+from pandas.util._decorators import cache_readonly
 
-from pandas._libs.algos import unique_deltas
+from pandas.core.dtypes.common import (
+    is_datetime64_dtype, is_period_arraylike, is_timedelta64_dtype)
+from pandas.core.dtypes.generic import ABCSeries
 
-from pytz import AmbiguousTimeError
+from pandas.core.algorithms import unique
 
+from pandas.tseries.offsets import (  # noqa
+    BDay, BMonthBegin, BMonthEnd, BQuarterBegin, BQuarterEnd, BYearBegin,
+    BYearEnd, CDay, DateOffset, Day, Hour, Micro, Milli, Minute, MonthBegin,
+    MonthEnd, Nano, QuarterBegin, QuarterEnd, Second, Week, YearBegin, YearEnd,
+    prefix_mapping)
 
 RESO_NS = 0
 RESO_US = 1
@@ -54,14 +51,6 @@
 # ---------------------------------------------------------------------
 # Offset names ("time rules") and related functions
 
-from pandas._libs.tslibs.offsets import _offset_to_period_map  # noqa:E402
-from pandas.tseries.offsets import (Nano, Micro, Milli, Second,  # noqa
-                                    Minute, Hour,
-                                    Day, BDay, CDay, Week, MonthBegin,
-                                    MonthEnd, BMonthBegin, BMonthEnd,
-                                    QuarterBegin, QuarterEnd, BQuarterBegin,
-                                    BQuarterEnd, YearBegin, YearEnd,
-                                    BYearBegin, BYearEnd, prefix_mapping)
 try:
     cday = CDay()
 except NotImplementedError:
diff --git a/pandas/tseries/holiday.py b/pandas/tseries/holiday.py
index 0497a827e2e1b2..40e2b76672a4e0 100644
--- a/pandas/tseries/holiday.py
+++ b/pandas/tseries/holiday.py
@@ -1,13 +1,16 @@
+from datetime import datetime, timedelta
 import warnings
 
-from pandas import DateOffset, DatetimeIndex, Series, Timestamp
-from pandas.errors import PerformanceWarning
-from pandas.compat import add_metaclass
-from datetime import datetime, timedelta
-from dateutil.relativedelta import MO, TU, WE, TH, FR, SA, SU  # noqa
-from pandas.tseries.offsets import Easter, Day
+from dateutil.relativedelta import FR, MO, SA, SU, TH, TU, WE  # noqa
 import numpy as np
 
+from pandas.compat import add_metaclass
+from pandas.errors import PerformanceWarning
+
+from pandas import DateOffset, DatetimeIndex, Series, Timestamp
+
+from pandas.tseries.offsets import Day, Easter
+
 
 def next_monday(dt):
     """
diff --git a/pandas/tseries/offsets.py b/pandas/tseries/offsets.py
index 440a6a3558d9e5..ca81b3bcfef2a0 100644
--- a/pandas/tseries/offsets.py
+++ b/pandas/tseries/offsets.py
@@ -3,33 +3,24 @@
 import functools
 import operator
 
-from pandas.compat import range
-from pandas import compat
-import numpy as np
-
-from pandas.core.dtypes.generic import ABCPeriod
-from pandas.core.tools.datetimes import to_datetime
-
-# import after tools, dateutil check
 from dateutil.easter import easter
-from pandas._libs import tslibs, Timestamp, OutOfBoundsDatetime, Timedelta
-from pandas.util._decorators import cache_readonly
+import numpy as np
 
 from pandas._libs.tslibs import (
-    ccalendar, conversion,
-    frequencies as libfrequencies)
-from pandas._libs.tslibs.timedeltas import delta_to_nanoseconds
-import pandas._libs.tslibs.offsets as liboffsets
+    NaT, OutOfBoundsDatetime, Timedelta, Timestamp, ccalendar, conversion,
+    delta_to_nanoseconds, frequencies as libfrequencies, normalize_date,
+    offsets as liboffsets)
 from pandas._libs.tslibs.offsets import (
-    ApplyTypeError,
-    as_datetime, _is_normalized,
-    _get_calendar, _to_dt64,
-    apply_index_wraps,
-    roll_yearday,
-    shift_month,
-    BaseOffset)
+    ApplyTypeError, BaseOffset, _get_calendar, _is_normalized, _to_dt64,
+    apply_index_wraps, as_datetime, roll_yearday, shift_month)
+import pandas.compat as compat
+from pandas.compat import range
 from pandas.errors import AbstractMethodError
+from pandas.util._decorators import cache_readonly
 
+from pandas.core.dtypes.generic import ABCPeriod
+
+from pandas.core.tools.datetimes import to_datetime
 
 __all__ = ['Day', 'BusinessDay', 'BDay', 'CustomBusinessDay', 'CDay',
            'CBMonthEnd', 'CBMonthBegin',
@@ -60,8 +51,8 @@ def as_timestamp(obj):
 def apply_wraps(func):
     @functools.wraps(func)
     def wrapper(self, other):
-        if other is tslibs.NaT:
-            return tslibs.NaT
+        if other is NaT:
+            return NaT
         elif isinstance(other, (timedelta, Tick, DateOffset)):
             # timedelta path
             return func(self, other)
@@ -103,7 +94,7 @@ def wrapper(self, other):
 
             if self.normalize:
                 # normalize_date returns normal datetime
-                result = tslibs.normalize_date(result)
+                result = normalize_date(result)
 
             if tz is not None and result.tzinfo is None:
                 result = conversion.localize_pydatetime(result, tz)
diff --git a/setup.cfg b/setup.cfg
index 0214922585077e..e8db1308741aa5 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -20,7 +20,8 @@ ignore =
     E731,  # do not assign a lambda expression, use a def
     C406,  # Unnecessary list literal - rewrite as a dict literal.
     C408,  # Unnecessary dict call - rewrite as a literal.
-    C409   # Unnecessary list passed to tuple() - rewrite as a tuple literal.
+    C409,  # Unnecessary list passed to tuple() - rewrite as a tuple literal.
+    S001   # found modulo formatter (incorrect picks up mod operations)
 exclude =
     doc/sphinxext/*.py,
     doc/build/*.py,
@@ -113,7 +114,6 @@ skip=
     pandas/core/ops.py,
     pandas/core/categorical.py,
     pandas/core/api.py,
-    pandas/core/window.py,
     pandas/core/indexing.py,
     pandas/core/apply.py,
     pandas/core/generic.py,
@@ -258,26 +258,6 @@ skip=
     pandas/tests/arithmetic/test_datetime64.py,
     pandas/tests/arithmetic/conftest.py,
     pandas/tests/arithmetic/test_timedelta64.py,
-    pandas/tests/scalar/test_nat.py,
-    pandas/tests/scalar/timestamp/test_rendering.py,
-    pandas/tests/scalar/timestamp/test_timestamp.py,
-    pandas/tests/scalar/timestamp/test_timezones.py,
-    pandas/tests/scalar/timestamp/test_unary_ops.py,
-    pandas/tests/scalar/timestamp/test_arithmetic.py,
-    pandas/tests/scalar/timestamp/test_comparisons.py,
-    pandas/tests/scalar/period/test_asfreq.py,
-    pandas/tests/scalar/period/test_period.py,
-    pandas/tests/scalar/timedelta/test_construction.py,
-    pandas/tests/scalar/timedelta/test_timedelta.py,
-    pandas/tests/scalar/timedelta/test_arithmetic.py,
-    pandas/tests/scalar/interval/test_interval.py,
-    pandas/tests/tslibs/test_tslib.py,
-    pandas/tests/tslibs/test_period_asfreq.py,
-    pandas/tests/tslibs/test_timezones.py,
-    pandas/tests/tslibs/test_libfrequencies.py,
-    pandas/tests/tslibs/test_parsing.py,
-    pandas/tests/tslibs/test_array_to_datetime.py,
-    pandas/tests/tslibs/test_conversion.py,
     pandas/tests/internals/test_internals.py,
     pandas/tests/groupby/test_value_counts.py,
     pandas/tests/groupby/test_filters.py,
@@ -387,10 +367,6 @@ skip=
     pandas/tests/sparse/frame/conftest.py,
     pandas/tests/computation/test_compat.py,
     pandas/tests/computation/test_eval.py,
-    pandas/tseries/holiday.py,
-    pandas/tseries/converter.py,
-    pandas/tseries/offsets.py,
-    pandas/tseries/frequencies.py,
     pandas/plotting/_core.py,
     pandas/plotting/_style.py,
     pandas/plotting/_timeseries.py,