From 8839e1bafccc796ca41617af02c12aa68c452378 Mon Sep 17 00:00:00 2001
From: Simon Hawkins <simonjayhawkins@gmail.com>
Date: Fri, 13 Dec 2019 16:09:11 +0000
Subject: [PATCH] CLN: various lgtm.com cleanups

---
 pandas/core/apply.py                    |  1 -
 pandas/core/arrays/datetimes.py         |  1 -
 pandas/core/arrays/integer.py           |  3 ++-
 pandas/core/arrays/numpy_.py            |  8 ++++++++
 pandas/core/arrays/sparse/dtype.py      |  7 +++++++
 pandas/core/arrays/timedeltas.py        |  1 -
 pandas/core/dtypes/base.py              |  2 +-
 pandas/core/dtypes/dtypes.py            | 15 +++++++++++----
 pandas/core/frame.py                    |  1 -
 pandas/core/generic.py                  |  2 --
 pandas/core/groupby/grouper.py          |  2 +-
 pandas/core/indexes/base.py             |  2 --
 pandas/core/internals/blocks.py         |  1 -
 pandas/core/reshape/reshape.py          |  2 --
 pandas/plotting/_matplotlib/hist.py     |  2 +-
 pandas/tests/arrays/test_array.py       |  7 +++++++
 pandas/tests/extension/arrow/arrays.py  | 14 ++++++++++++++
 pandas/tests/extension/decimal/array.py |  3 ++-
 pandas/tests/extension/json/array.py    |  3 ++-
 19 files changed, 56 insertions(+), 21 deletions(-)

diff --git a/pandas/core/apply.py b/pandas/core/apply.py
index ef3d8cd53596b..14a3c3c008e92 100644
--- a/pandas/core/apply.py
+++ b/pandas/core/apply.py
@@ -320,7 +320,6 @@ def apply_series_generator(self) -> Tuple[ResType, "Index"]:
         series_gen = self.series_generator
         res_index = self.result_index
 
-        i = None
         keys = []
         results = {}
         if self.ignore_failures:
diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py
index 2cd8aafe00f37..e41f2a840d151 100644
--- a/pandas/core/arrays/datetimes.py
+++ b/pandas/core/arrays/datetimes.py
@@ -2109,7 +2109,6 @@ def _validate_dt64_dtype(dtype):
         dtype = pandas_dtype(dtype)
         if is_dtype_equal(dtype, np.dtype("M8")):
             # no precision, disallowed GH#24806
-            dtype = _NS_DTYPE
             msg = (
                 "Passing in 'datetime64' dtype with no precision is not allowed. "
                 "Please pass in 'datetime64[ns]' instead."
diff --git a/pandas/core/arrays/integer.py b/pandas/core/arrays/integer.py
index d47e7e3df27e1..c0ca30be34ad5 100644
--- a/pandas/core/arrays/integer.py
+++ b/pandas/core/arrays/integer.py
@@ -78,7 +78,8 @@ def itemsize(self):
 
     @classmethod
     def construct_array_type(cls):
-        """Return the array type associated with this dtype
+        """
+        Return the array type associated with this dtype.
 
         Returns
         -------
diff --git a/pandas/core/arrays/numpy_.py b/pandas/core/arrays/numpy_.py
index 13748e03e856d..deec30dfe34ff 100644
--- a/pandas/core/arrays/numpy_.py
+++ b/pandas/core/arrays/numpy_.py
@@ -79,7 +79,15 @@ def construct_from_string(cls, string):
                 f"Cannot construct a 'PandasDtype' from '{string}'"
             ) from err
 
+    @classmethod
     def construct_array_type(cls):
+        """
+        Return the array type associated with this dtype.
+
+        Returns
+        -------
+        type
+        """
         return PandasArray
 
     @property
diff --git a/pandas/core/arrays/sparse/dtype.py b/pandas/core/arrays/sparse/dtype.py
index a295dfed2cf96..935f657416396 100644
--- a/pandas/core/arrays/sparse/dtype.py
+++ b/pandas/core/arrays/sparse/dtype.py
@@ -168,6 +168,13 @@ def __repr__(self) -> str:
 
     @classmethod
     def construct_array_type(cls):
+        """
+        Return the array type associated with this dtype.
+
+        Returns
+        -------
+        type
+        """
         from .array import SparseArray
 
         return SparseArray
diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index b51773961811b..db4effa608582 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -1122,7 +1122,6 @@ def _validate_td64_dtype(dtype):
     dtype = pandas_dtype(dtype)
     if is_dtype_equal(dtype, np.dtype("timedelta64")):
         # no precision disallowed GH#24806
-        dtype = _TD_DTYPE
         msg = (
             "Passing in 'timedelta' dtype with no precision is not allowed. "
             "Please pass in 'timedelta64[ns]' instead."
diff --git a/pandas/core/dtypes/base.py b/pandas/core/dtypes/base.py
index ae544376c452e..1dda51da49ffb 100644
--- a/pandas/core/dtypes/base.py
+++ b/pandas/core/dtypes/base.py
@@ -183,7 +183,7 @@ def names(self) -> Optional[List[str]]:
     @classmethod
     def construct_array_type(cls):
         """
-        Return the array type associated with this dtype
+        Return the array type associated with this dtype.
 
         Returns
         -------
diff --git a/pandas/core/dtypes/dtypes.py b/pandas/core/dtypes/dtypes.py
index 4421fad5f19d1..77ec182be5ed4 100644
--- a/pandas/core/dtypes/dtypes.py
+++ b/pandas/core/dtypes/dtypes.py
@@ -486,7 +486,7 @@ def _hash_categories(categories, ordered: Ordered = True) -> int:
     @classmethod
     def construct_array_type(cls):
         """
-        Return the array type associated with this dtype
+        Return the array type associated with this dtype.
 
         Returns
         -------
@@ -668,7 +668,7 @@ def __init__(self, unit="ns", tz=None):
                 unit = result.unit
                 tz = result.tz
                 msg = (
-                    "Passing a dtype alias like 'datetime64[ns, {tz}]' "
+                    f"Passing a dtype alias like 'datetime64[ns, {tz}]' "
                     "to DatetimeTZDtype is no longer supported. Use "
                     "'DatetimeTZDtype.construct_from_string()' instead."
                 )
@@ -704,7 +704,7 @@ def tz(self):
     @classmethod
     def construct_array_type(cls):
         """
-        Return the array type associated with this dtype
+        Return the array type associated with this dtype.
 
         Returns
         -------
@@ -936,6 +936,13 @@ def is_dtype(cls, dtype) -> bool:
 
     @classmethod
     def construct_array_type(cls):
+        """
+        Return the array type associated with this dtype.
+
+        Returns
+        -------
+        type
+        """
         from pandas.core.arrays import PeriodArray
 
         return PeriodArray
@@ -1030,7 +1037,7 @@ def subtype(self):
     @classmethod
     def construct_array_type(cls):
         """
-        Return the array type associated with this dtype
+        Return the array type associated with this dtype.
 
         Returns
         -------
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index fa85c54eb42fa..0c5caac36054e 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -2606,7 +2606,6 @@ def _ixs(self, i: int, axis: int = 0):
         """
         # irow
         if axis == 0:
-            label = self.index[i]
             new_values = self._data.fast_xs(i)
 
             # if we are a copy, mark as such
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index cf2244b4df4d2..4508f02757def 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -5746,8 +5746,6 @@ def __deepcopy__(self: FrameOrSeries, memo=None) -> FrameOrSeries:
         memo, default None
             Standard signature. Unused
         """
-        if memo is None:
-            memo = {}
         return self.copy(deep=True)
 
     def _convert(
diff --git a/pandas/core/groupby/grouper.py b/pandas/core/groupby/grouper.py
index b0df04f18ff1d..63d6e88850cdd 100644
--- a/pandas/core/groupby/grouper.py
+++ b/pandas/core/groupby/grouper.py
@@ -131,7 +131,7 @@ def _get_grouper(self, obj, validate: bool = True):
         """
 
         self._set_grouper(obj)
-        self.grouper, exclusions, self.obj = get_grouper(
+        self.grouper, _, self.obj = get_grouper(
             self.obj,
             [self.key],
             axis=self.axis,
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index fc2412ceaca0e..22dd25c0448d2 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -910,8 +910,6 @@ def __deepcopy__(self, memo=None):
         memo, default None
             Standard signature. Unused
         """
-        if memo is None:
-            memo = {}
         return self.copy(deep=True)
 
     # --------------------------------------------------------------------
diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index 8a543832b50fe..610a39a05148b 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -3024,7 +3024,6 @@ def _merge_blocks(blocks, dtype=None, _can_consolidate=True):
         if dtype is None:
             if len({b.dtype for b in blocks}) != 1:
                 raise AssertionError("_merge_blocks are invalid!")
-            dtype = blocks[0].dtype
 
         # FIXME: optimization potential in case all mgrs contain slices and
         # combination of those slices is a slice, too.
diff --git a/pandas/core/reshape/reshape.py b/pandas/core/reshape/reshape.py
index a8dcc995e48da..b74eda38a08fe 100644
--- a/pandas/core/reshape/reshape.py
+++ b/pandas/core/reshape/reshape.py
@@ -230,11 +230,9 @@ def get_new_values(self):
         if needs_i8_conversion(values):
             sorted_values = sorted_values.view("i8")
             new_values = new_values.view("i8")
-            name = "int64"
         elif is_bool_dtype(values):
             sorted_values = sorted_values.astype("object")
             new_values = new_values.astype("object")
-            name = "object"
         else:
             sorted_values = sorted_values.astype(name, copy=False)
 
diff --git a/pandas/plotting/_matplotlib/hist.py b/pandas/plotting/_matplotlib/hist.py
index dc9eede7e4d52..8957389ac2b13 100644
--- a/pandas/plotting/_matplotlib/hist.py
+++ b/pandas/plotting/_matplotlib/hist.py
@@ -27,7 +27,7 @@ def _args_adjust(self):
             values = np.ravel(values)
             values = values[~isna(values)]
 
-            hist, self.bins = np.histogram(
+            _, self.bins = np.histogram(
                 values,
                 bins=self.bins,
                 range=self.kwds.get("range", None),
diff --git a/pandas/tests/arrays/test_array.py b/pandas/tests/arrays/test_array.py
index 479f8dbad0418..f2a4e73e7b6ad 100644
--- a/pandas/tests/arrays/test_array.py
+++ b/pandas/tests/arrays/test_array.py
@@ -287,6 +287,13 @@ class DecimalDtype2(DecimalDtype):
 
     @classmethod
     def construct_array_type(cls):
+        """
+        Return the array type associated with this dtype.
+
+        Returns
+        -------
+        type
+        """
         return DecimalArray2
 
 
diff --git a/pandas/tests/extension/arrow/arrays.py b/pandas/tests/extension/arrow/arrays.py
index 86e23b3264456..b0e5a6f85feeb 100644
--- a/pandas/tests/extension/arrow/arrays.py
+++ b/pandas/tests/extension/arrow/arrays.py
@@ -37,6 +37,13 @@ def construct_from_string(cls, string):
 
     @classmethod
     def construct_array_type(cls):
+        """
+        Return the array type associated with this dtype.
+
+        Returns
+        -------
+        type
+        """
         return ArrowBoolArray
 
     def _is_boolean(self):
@@ -60,6 +67,13 @@ def construct_from_string(cls, string):
 
     @classmethod
     def construct_array_type(cls):
+        """
+        Return the array type associated with this dtype.
+
+        Returns
+        -------
+        type
+        """
         return ArrowStringArray
 
 
diff --git a/pandas/tests/extension/decimal/array.py b/pandas/tests/extension/decimal/array.py
index 0b0865c424f34..74f1e3cfbaf20 100644
--- a/pandas/tests/extension/decimal/array.py
+++ b/pandas/tests/extension/decimal/array.py
@@ -27,7 +27,8 @@ def __repr__(self) -> str:
 
     @classmethod
     def construct_array_type(cls):
-        """Return the array type associated with this dtype
+        """
+        Return the array type associated with this dtype.
 
         Returns
         -------
diff --git a/pandas/tests/extension/json/array.py b/pandas/tests/extension/json/array.py
index 28929d50718b6..46ca7bd8f760a 100644
--- a/pandas/tests/extension/json/array.py
+++ b/pandas/tests/extension/json/array.py
@@ -31,7 +31,8 @@ class JSONDtype(ExtensionDtype):
 
     @classmethod
     def construct_array_type(cls):
-        """Return the array type associated with this dtype
+        """
+        Return the array type associated with this dtype.
 
         Returns
         -------