Use isinstance() to provide a hint to Mypy

pottery/base.py

@@ -156,10 +156,10 @@ def _encode(decoded_value: JSONTypes) -> str:
     @final
     @staticmethod
     def _decode(encoded_value: AnyStr) -> JSONTypes:
-        try:
-            string = cast(bytes, encoded_value).decode('utf-8')
-        except AttributeError:
-            string = cast(str, encoded_value)
+        if isinstance(encoded_value, bytes):
+            string = encoded_value.decode('utf-8')
+        else:
+            string = encoded_value
         decoded_value: JSONTypes = json.loads(string)
         return decoded_value
 

pottery/cache.py

@@ -17,7 +17,6 @@
 
 
 import collections
-import contextlib
 import functools
 import itertools
 from typing import Any
@@ -44,7 +43,6 @@
 from .base import random_key
 from .dict import InitArg
 from .dict import InitIter
-from .dict import InitMap
 from .dict import RedisDict
 
 
@@ -330,8 +328,8 @@ def update(self, arg: InitArg = tuple(), **kwargs: JSONTypes) -> None:  # type:
         makes a single bulk call to Redis.
         '''
         to_cache = {}
-        with contextlib.suppress(AttributeError):
-            arg = cast(InitMap, arg).items()
+        if isinstance(arg, collections.abc.Mapping):
+            arg = arg.items()
         items = itertools.chain(cast(InitIter, arg), kwargs.items())
         for dict_key, value in items:
             if value is not self._SENTINEL:

pottery/counter.py

@@ -58,11 +58,11 @@ def _populate(self,  # type: ignore
                   **kwargs: int,
                   ) -> None:
         dict_ = {}
-        try:
-            items = cast(Counter[JSONTypes], arg).items()
+        if isinstance(arg, collections.abc.Mapping):
+            items = arg.items()
             for key, value in items:
                 dict_[key] = sign * value
-        except AttributeError:
+        else:
             for key in arg:
                 value = dict_.get(key, self[key])
                 dict_[key] = value + sign
@@ -180,7 +180,7 @@ def __imath_op(self,
                    ) -> RedisCounter:
         with self._watch(other) as pipeline:
             try:
-                other_items = cast('RedisCounter', other).to_counter().items()
+                other_items = cast(RedisCounter, other).to_counter().items()
             except AttributeError:
                 other_items = other.items()
             to_set = {k: self[k] + sign * v for k, v in other_items}
@@ -217,7 +217,7 @@ def __iset_op(self,
         with self._watch(other) as pipeline:
             self_counter = self.__to_counter()
             try:
-                other_counter = cast('RedisCounter', other).to_counter()
+                other_counter = cast(RedisCounter, other).to_counter()
             except AttributeError:
                 other_counter = other
             to_set, to_del = {}, set()

pottery/dict.py

@@ -17,7 +17,6 @@
 
 
 import collections.abc
-import contextlib
 import itertools
 import warnings
 from typing import Any
@@ -69,9 +68,9 @@ def _populate(self,
                   arg: InitArg = tuple(),
                   **kwargs: JSONTypes,
                   ) -> None:
-        with contextlib.suppress(AttributeError):
-            arg = cast(InitMap, arg).items()
-        items = itertools.chain(cast(InitIter, arg), kwargs.items())
+        if isinstance(arg, collections.abc.Mapping):
+            arg = arg.items()
+        items = itertools.chain(arg, kwargs.items())
         dict_ = dict(items)
         encoded_dict = self.__encode_dict(dict_)
         if encoded_dict:

pottery/nextid.py

@@ -180,7 +180,7 @@ def __current_id(self) -> int:
             current_ids, redis_errors = [], []
             for future in concurrent.futures.as_completed(futures):
                 try:
-                    current_id = int(cast(bytes, future.result() or b'0'))
+                    current_id = int(future.result() or b'0')
                 except RedisError as error:
                     redis_errors.append(error)
                     logger.exception(