Inherit from ABC rather than setting metaclass

Author: cburgdorf

evm/chains/base.py

@@ -1,7 +1,7 @@
 from __future__ import absolute_import
 
 from abc import (
-    ABCMeta,
+    ABC,
     abstractmethod
 )
 import operator
@@ -102,7 +102,7 @@
 AccountState = Dict[Address, Dict[str, Union[int, bytes, Dict[int, int]]]]
 
 
-class BaseChain(Configurable, metaclass=ABCMeta):
+class BaseChain(Configurable, ABC):
     """
     The base class for all Chain objects
     """

evm/chains/header.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from typing import Dict, Any, Tuple, Type  # noqa: F401
 
 from eth_typing import (
@@ -18,7 +18,7 @@
 from evm.vm.base import BaseVM  # noqa: F401
 
 
-class BaseHeaderChain(Configurable, metaclass=ABCMeta):
+class BaseHeaderChain(Configurable, ABC):
     _base_db = None  # type: BaseDB
 
     _headerdb_class = None  # type: Type[BaseHeaderDB]

evm/db/account.py

@@ -1,5 +1,5 @@
 from abc import (
-    ABCMeta,
+    ABC,
     abstractmethod
 )
 from uuid import UUID
@@ -59,7 +59,7 @@
 account_cache = LRU(2048)
 
 
-class BaseAccountDB(metaclass=ABCMeta):
+class BaseAccountDB(ABC):
 
     @abstractmethod
     def __init__(self) -> None:

evm/db/backends/base.py

@@ -1,13 +1,13 @@
 from abc import (
-    ABCMeta,
+    ABC,
     abstractmethod
 )
 from collections.abc import (
     MutableMapping,
 )
 
 
-class BaseDB(MutableMapping, metaclass=ABCMeta):
+class BaseDB(MutableMapping, ABC):
     """
     This is an abstract key/value lookup with all :class:`bytes` values,
     with some convenience methods for databases. As much as possible,

evm/db/chain.py

@@ -2,7 +2,7 @@
 import itertools
 
 from abc import (
-    ABCMeta,
+    ABC,
     abstractmethod
 )
 from typing import (
@@ -76,7 +76,7 @@ class TransactionKey(rlp.Serializable):
     ]
 
 
-class BaseChainDB(metaclass=ABCMeta):
+class BaseChainDB(ABC):
     db = None  # type: BaseDB
 
     @abstractmethod

evm/db/header.py

@@ -1,4 +1,4 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 from typing import Tuple, Iterable
 
 import rlp
@@ -30,7 +30,7 @@
 )
 
 
-class BaseHeaderDB(metaclass=ABCMeta):
+class BaseHeaderDB(ABC):
     db = None  # type: BaseDB
 
     def __init__(self, db: BaseDB) -> None:

evm/db/schema.py

@@ -1,12 +1,12 @@
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 
 from eth_typing import (
     BlockNumber,
     Hash32,
 )
 
 
-class BaseSchema(metaclass=ABCMeta):
+class BaseSchema(ABC):
     @staticmethod
     @abstractmethod
     def make_canonical_head_hash_lookup_key() -> bytes:

evm/rlp/blocks.py

@@ -1,5 +1,5 @@
 from abc import (
-    ABCMeta,
+    ABC,
     abstractmethod
 )
 from typing import (  # noqa: F401
@@ -22,7 +22,7 @@
 from .headers import BlockHeader
 
 
-class BaseBlock(rlp.Serializable, Configurable, metaclass=ABCMeta):
+class BaseBlock(rlp.Serializable, Configurable, ABC):
     transaction_class = None  # type: Type[BaseTransaction]
 
     @classmethod

evm/rlp/transactions.py

@@ -1,5 +1,5 @@
 from abc import (
-    ABCMeta,
+    ABC,
     abstractmethod
 )
 from typing import (
@@ -154,7 +154,7 @@ def create_unsigned_transaction(self, *args: Any, **kwargs: Any) -> 'BaseTransac
         raise NotImplementedError("Must be implemented by subclasses")
 
 
-class BaseUnsignedTransaction(rlp.Serializable, BaseTransactionCommonMethods, metaclass=ABCMeta):
+class BaseUnsignedTransaction(rlp.Serializable, BaseTransactionCommonMethods, ABC):
     fields = [
         ('nonce', big_endian_int),
         ('gas_price', big_endian_int),

evm/vm/base.py

@@ -1,6 +1,6 @@
 from __future__ import absolute_import
 from abc import (
-    ABCMeta,
+    ABC,
     abstractmethod,
 )
 import contextlib
@@ -63,7 +63,7 @@
 from evm.vm.state import BaseState  # noqa: F401
 
 
-class BaseVM(Configurable, metaclass=ABCMeta):
+class BaseVM(Configurable, ABC):
     block = None  # type: BaseBlock
     block_class = None  # type: Type[BaseBlock]
     fork = None  # type: str